diff --git a/CMakeLists.txt b/CMakeLists.txt
index 71f6e19..e7aea20 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,6 +1,8 @@
 cmake_minimum_required(VERSION 3.5)
 project(cgbwebcam)
 
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
 set(SDL_STATIC ON)
 set(SDL_SHARED OFF)
 
diff --git a/main.c b/main.c
index 8fd1d67..d42fd19 100644
--- a/main.c
+++ b/main.c
@@ -1,3 +1,4 @@
+#include "SDL_blendmode.h"
 #include "SDL_error.h"
 #include "SDL_stdinc.h"
 #include "SDL_surface.h"
@@ -17,19 +18,21 @@
 #include "mgba/feature/commandline.h"
 #include "mgba-util/image.h"
 
+#define NUM_CHANNELS 3
+
 static SDL_Window* window = NULL;
 static SDL_Renderer* renderer = NULL;
 static SDL_Camera* camera = NULL;
 static SDL_CameraSpec spec;
-static SDL_Texture* texture = NULL;
+static SDL_Texture* textures[NUM_CHANNELS] = { NULL, NULL, NULL };
 static SDL_bool texture_updated = SDL_FALSE;
-static SDL_Surface* frame_current = NULL;
 static SDL_CameraDeviceID front_camera = 0;
 static SDL_CameraDeviceID back_camera = 0;
 static SDL_Surface* scaled = NULL;
-static SDL_Surface* screen = NULL;
+static SDL_Surface* filtered[NUM_CHANNELS] = { NULL, NULL, NULL };
+static SDL_Surface* screens[NUM_CHANNELS] = { NULL, NULL, NULL };
 
-static struct mCore* core = NULL;
+static struct mCore* cores[NUM_CHANNELS] = { NULL, NULL, NULL };
 
 enum mColorFormat pixfmt_sdl_to_mgba(uint32_t sdl_fmt) {
     switch (sdl_fmt) {
@@ -54,47 +57,90 @@ enum mColorFormat pixfmt_sdl_to_mgba(uint32_t sdl_fmt) {
     }
 }
 
-void myStartRequestImage(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
+void myStartRequestImageRed(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
     SDL_DestroySurface(scaled);
+    SDL_DestroySurface(filtered[0]);
     scaled = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
+    filtered[0] = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
 
-    SDL_Log("scaled: %d x %d", w, h);
+    SDL_Log("red: %d x %d", w, h);
     
 //    SDL_DestroyTexture(texture);
 //    texture = SDL_CreateTextureFromSurface(renderer, scaled);
 }
 
-void myStopRequestImage(struct mImageSource* self) {
-    SDL_DestroySurface(scaled);
-    scaled = NULL;
+void myStartRequestImageGreen(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
+    SDL_DestroySurface(filtered[1]);
+    filtered[1] = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
+    SDL_Log("green: %d x %d", w, h);
 }
 
-void myRequestImage(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
-    if (scaled != NULL && frame_current != NULL) {
-        struct SDL_Rect srcrect = frame_current->clip_rect;
-        int w = srcrect.h * scaled->clip_rect.w / scaled->clip_rect.h;
-        if (w >= srcrect.w) {
-            srcrect.x = (srcrect.w - w) / 2;
-            srcrect.w = w;
-        } else {
-            int h = srcrect.w * scaled->clip_rect.h / scaled->clip_rect.w;
-            srcrect.y = (srcrect.h - h) / 2;
-            srcrect.h = h;
-        }
-        int res = SDL_BlitSurfaceScaled(frame_current, &srcrect, scaled, &scaled->clip_rect, SDL_SCALEMODE_NEAREST);
-        if (res != 0) {
-            SDL_Log("failed to scale: %s", SDL_GetError());
-        }
-        *fmt = pixfmt_sdl_to_mgba(scaled->format->format);
-        *stride = scaled->pitch / (BYTES_PER_PIXEL / scaled->format->bytes_per_pixel);
-        *buf = scaled->pixels;
+void myStartRequestImageBlue(struct mImageSource* self, unsigned w, unsigned h, int colorFormats) {
+    SDL_DestroySurface(filtered[2]);
+    filtered[2] = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
+    SDL_Log("blue: %d x %d", w, h);
+}
+
+void myStopRequestImageRed(struct mImageSource* self) {
+    SDL_DestroySurface(scaled);
+    SDL_DestroySurface(filtered[0]);
+    scaled = NULL;
+    filtered[0] = NULL;
+}
+
+void myStopRequestImageGreen(struct mImageSource* self) {
+    SDL_DestroySurface(filtered[1]);
+    filtered[1] = NULL;
+}
+
+void myStopRequestImageBlue(struct mImageSource* self) {
+    SDL_DestroySurface(filtered[2]);
+    filtered[2] = NULL;
+}
+
+void myRequestImageRed(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
+    SDL_Surface* source = filtered[0];
+    if (source != NULL) {
+        *fmt = pixfmt_sdl_to_mgba(source->format->format);
+        *stride = source->pitch / (BYTES_PER_PIXEL / source->format->bytes_per_pixel);
+        *buf = source->pixels;
     }
 }
 
-const struct mImageSource gb_img_src = {
-    .requestImage = myRequestImage,
-    .startRequestImage = myStartRequestImage,
-    .stopRequestImage = myStopRequestImage,
+void myRequestImageGreen(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
+    SDL_Surface* source = filtered[1];
+    if (source != NULL) {
+        *fmt = pixfmt_sdl_to_mgba(source->format->format);
+        *stride = source->pitch / (BYTES_PER_PIXEL / source->format->bytes_per_pixel);
+        *buf = source->pixels;
+    }
+}
+
+void myRequestImageBlue(struct mImageSource* self, const void** buf, size_t* stride, enum mColorFormat* fmt) {
+    SDL_Surface* source = filtered[2];
+    if (source != NULL) {
+        *fmt = pixfmt_sdl_to_mgba(source->format->format);
+        *stride = source->pitch / (BYTES_PER_PIXEL / source->format->bytes_per_pixel);
+        *buf = source->pixels;
+    }
+}
+
+const struct mImageSource gb_img_src[3] = {
+    {
+        .requestImage = myRequestImageRed,
+        .startRequestImage = myStartRequestImageRed,
+        .stopRequestImage = myStopRequestImageRed,
+    },
+    {
+        .requestImage = myRequestImageGreen,
+        .startRequestImage = myStartRequestImageGreen,
+        .stopRequestImage = myStopRequestImageGreen,
+    },
+    {
+        .requestImage = myRequestImageBlue,
+        .startRequestImage = myStartRequestImageBlue,
+        .stopRequestImage = myStopRequestImageBlue,
+    },
 };
 
 int SDL_AppInit(int argc, char *argv[]) {
@@ -112,28 +158,33 @@ int SDL_AppInit(int argc, char *argv[]) {
         return -1;
     }
 
-    core = mCoreFind(args.fname);
-    if (!core || !core->init(core)) {
-        SDL_Log("Couldn't initialize mgba core!");
-        return -1;
+    for (i = 0; i < NUM_CHANNELS; i++) {
+        struct mCore* core = mCoreFind(args.fname);
+        if (!core || !core->init(core)) {
+            SDL_Log("Couldn't initialize mgba core!");
+            return -1;
+        }
+
+        if (!mCoreLoadFile(core, args.fname)) {
+            SDL_Log("Failed to load ROM");
+            return -1;
+        }
+
+        mCoreConfigInit(&core->config, NULL);
+        //mCoreConfigLoad(&core->config);
+
+        mArgumentsApply(&args, NULL, 0, &core->config);
+        mCoreConfigSetDefaultValue(&core->config, "idleOptimization", "detect");
+        mCoreConfigSetDefaultValue(&core->config, "sgb.borders", "0");
+
+        mCoreLoadConfig(core);
+
+        cores[i] = core;
     }
 
-    if (!mCoreLoadFile(core, args.fname)) {
-        SDL_Log("Failed to load ROM");
-        return -1;
-    }
-
-    mCoreConfigInit(&core->config, NULL);
-    //mCoreConfigLoad(&core->config);
-
-    mArgumentsApply(&args, NULL, 0, &core->config);
-    mCoreConfigSetDefaultValue(&core->config, "idleOptimization", "detect");
-    mCoreConfigSetDefaultValue(&core->config, "sgb.borders", "0");
-
-    mCoreLoadConfig(core);
-
     unsigned w, h;
-    core->currentVideoSize(core, &w, &h);
+    // without loss of generality
+    cores[0]->currentVideoSize(cores[0], &w, &h);
 
     if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_CAMERA) != 0) {
         SDL_Log("Couldn't initialize SDL3: %s", SDL_GetError());
@@ -185,61 +236,76 @@ int SDL_AppInit(int argc, char *argv[]) {
         return -1;
     }
 
-    SDL_CameraSpec spec = {
+    SDL_CameraSpec init_spec = {
         .format = SDL_PIXELFORMAT_XBGR1555,
         .width = 320,
         .height = 240,
         .interval_numerator = 1,
         .interval_denominator = 30,
     };
-    camera = SDL_OpenCameraDevice(devid, &spec);
+    camera = SDL_OpenCameraDevice(devid, &init_spec);
     if (!camera) {
         SDL_Log("Failed to open camera device: %s", SDL_GetError());
         return -1;
     }
 
 #if BYTES_PER_PIXEL == 4
-    screen = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR8888);
+    uint32_t fmt = SDL_PIXELFORMAT_XBGR8888;
 #elif BYTES_PER_PIXEL == 2
-    screen = SDL_CreateSurface(w, h, SDL_PIXELFORMAT_XBGR1555);
+    uint32_t fmt = SDL_PIXELFORMAT_XBGR1555;
 #else
     #error "unknown pixel format"
 #endif
-    core->setVideoBuffer(core, screen->pixels, screen->pitch / BYTES_PER_PIXEL);
+    for (i = 0; i < NUM_CHANNELS; i++) {
+        int j;
+        struct mCore* core = cores[i];
 
-    /* Create texture with appropriate format */
-    texture = SDL_CreateTextureFromSurface(renderer, screen);
-    if (!texture) {
-        SDL_Log("Couldn't create texture: %s", SDL_GetError());
-        return -1;
+        SDL_Surface* screen = SDL_CreateSurface(w, h, fmt);
+        core->setVideoBuffer(core, screen->pixels, screen->pitch / BYTES_PER_PIXEL);
+        screens[i] = screen;
+
+        /* Create texture with appropriate format */
+        SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, screens[0]);
+        if (!texture) {
+            SDL_Log("Couldn't create texture: %s", SDL_GetError());
+            return -1;
+        }
+        SDL_SetTextureBlendMode(texture, SDL_BLENDMODE_ADD);
+        textures[i] = texture;
+
+        core->setPeripheral(core, mPERIPH_IMAGE_SOURCE, (void*)&gb_img_src[i]);
+
+        core->reset(core);
+
+        core->setKeys(core, 0);
+        for (j = 0; j < 600; j++) {
+            core->runFrame(core);
+        }
+        core->setKeys(core, 1); // title screen
+        core->runFrame(core);
+        core->setKeys(core, 0);
+        for (j = 0; j < 25; j++) {
+            core->runFrame(core);
+        }
+        core->setKeys(core, 1); // select 'shoot'
+        core->runFrame(core);
+        core->setKeys(core, 0);
+        for (j = 0; j < 75; j++) {
+            core->runFrame(core);
+        }
+        core->setKeys(core, 1); // select 'shoot' again
+        core->runFrame(core);
+        core->setKeys(core, 0);
+        for (j = 0; j < 100; j++) {
+            core->runFrame(core);
+        }
+
+        SDL_Log("prepared core %d", i);
     }
 
-    core->setPeripheral(core, mPERIPH_IMAGE_SOURCE, (void*)&gb_img_src);
-
-    core->reset(core);
-
-    core->setKeys(core, 0);
-    for (i = 0; i < 600; i++) {
-        core->runFrame(core);
-    }
-    core->setKeys(core, 1); // title screen
-    core->runFrame(core);
-    core->setKeys(core, 0);
-    for (i = 0; i < 25; i++) {
-        core->runFrame(core);
-    }
-    core->setKeys(core, 1); // select 'shoot'
-    core->runFrame(core);
-    core->setKeys(core, 0);
-    for (i = 0; i < 75; i++) {
-        core->runFrame(core);
-    }
-    core->setKeys(core, 1); // select 'shoot' again
-    core->runFrame(core);
-    core->setKeys(core, 0);
-    for (i = 0; i < 100; i++) {
-        core->runFrame(core);
-    }
+    SDL_SetTextureColorMod(textures[0], 255, 0, 0);
+    SDL_SetTextureColorMod(textures[1], 0, 255, 0);
+    SDL_SetTextureColorMod(textures[2], 0, 0, 255);
 
     return 0;  /* start the main app loop. */
 }
@@ -262,11 +328,6 @@ static int FlipCamera(void) {
         if (nextcam) {
             SDL_Log("Flip camera!");
 
-            if (frame_current) {
-                SDL_ReleaseCameraFrame(camera, frame_current);
-                frame_current = NULL;
-            }
-
             SDL_CloseCamera(camera);
 
             camera = SDL_OpenCameraDevice(nextcam, NULL);
@@ -321,49 +382,77 @@ int SDL_AppEvent(const SDL_Event *event) {
 }
 
 int SDL_AppIterate(void) {
-    SDL_SetRenderDrawColor(renderer, 0x99, 0x99, 0x99, 255);
-    SDL_RenderClear(renderer);
+    int i;
 
-    Uint64 timestampNS = 0;
-    SDL_Surface *frame_next = camera ? SDL_AcquireCameraFrame(camera, &timestampNS) : NULL;
+    if (scaled != NULL) {
+        Uint64 timestampNS = 0;
+        SDL_Surface *frame = camera ? SDL_AcquireCameraFrame(camera, &timestampNS) : NULL;
 
-    if (frame_next) {
-        if (frame_current) {
-            if (SDL_ReleaseCameraFrame(camera, frame_current) < 0) {
+        if (frame) {
+            //SDL_Log("new frame %d x %d %s", frame->w, frame->h, SDL_GetPixelFormatName(frame->format->format));
+            texture_updated = SDL_FALSE;
+
+            struct SDL_Rect srcrect = frame->clip_rect;
+            int w = srcrect.h * scaled->clip_rect.w / scaled->clip_rect.h;
+            if (w >= srcrect.w) {
+                srcrect.x = (srcrect.w - w) / 2;
+                srcrect.w = w;
+            } else {
+                int h = srcrect.w * scaled->clip_rect.h / scaled->clip_rect.w;
+                srcrect.y = (srcrect.h - h) / 2;
+                srcrect.h = h;
+            }
+            int res = SDL_BlitSurfaceScaled(frame, &srcrect, scaled, &scaled->clip_rect, SDL_SCALEMODE_NEAREST);
+            if (res != 0) {
+                SDL_Log("failed to scale: %s", SDL_GetError());
+            }
+
+            if (SDL_ReleaseCameraFrame(camera, frame) < 0) {
                 SDL_Log("err SDL_ReleaseCameraFrame: %s", SDL_GetError());
             }
+
+            SDL_SetSurfaceColorMod(scaled, 255, 0, 0);
+            SDL_BlitSurface(scaled, NULL, filtered[0], NULL);
+            SDL_SetSurfaceColorMod(scaled, 0, 255, 0);
+            SDL_BlitSurface(scaled, NULL, filtered[1], NULL);
+            SDL_SetSurfaceColorMod(scaled, 0, 0, 255);
+            SDL_BlitSurface(scaled, NULL, filtered[2], NULL);
+        }
+    }
+
+    for (i = 0; i < NUM_CHANNELS; i++) {
+        struct mCore* core = cores[i];
+        core->runFrame(core);
+    }
+
+    if (!texture_updated) {
+        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+        SDL_RenderClear(renderer);
+
+        /* Update SDL_Texture with last video frame (only once per new frame) */
+        for (i = 0; i < NUM_CHANNELS; i++) {
+            SDL_Surface* screen = screens[i];
+            SDL_Texture* texture = textures[i];
+            SDL_UpdateTexture(texture, NULL, screen->pixels, screen->pitch);
+            texture_updated = SDL_TRUE;
+            SDL_RenderTexture(renderer, texture, NULL, NULL);
         }
 
-        SDL_Log("new frame %d x %d %s", frame_next->w, frame_next->h, SDL_GetPixelFormatName(frame_next->format->format));
-        
-        /* It's not needed to keep the frame once updated the texture is updated.
-         * But in case of 0-copy, it's needed to have the frame while using the texture.
-         */
-         frame_current = frame_next;
-         texture_updated = SDL_FALSE;
+        SDL_RenderPresent(renderer);
     }
 
-    core->runFrame(core);
-    /* Update SDL_Texture with last video frame (only once per new frame) */
-    if (frame_current && !texture_updated) {
-//        if (scaled) SDL_UpdateTexture(texture, NULL, scaled->pixels, scaled->pitch);
-        SDL_UpdateTexture(texture, NULL, screen->pixels, screen->pitch);
-        texture_updated = SDL_TRUE;
-    }
-
-    SDL_RenderTexture(renderer, texture, NULL, NULL);
-    SDL_RenderPresent(renderer);
-
     return 0;  /* keep iterating. */
 }
 
 void SDL_AppQuit(void) {
-    mCoreConfigDeinit(&core->config);
-    core->deinit(core);
+    int i;
+    for (i = 0; i < NUM_CHANNELS; i++) {
+        mCoreConfigDeinit(&cores[i]->config);
+        cores[i]->deinit(cores[i]);
+        SDL_DestroyTexture(textures[i]);
+    }
 
-    SDL_ReleaseCameraFrame(camera, frame_current);
     SDL_CloseCamera(camera);
-    SDL_DestroyTexture(texture);
     SDL_DestroyRenderer(renderer);
     SDL_DestroyWindow(window);
 }