Skins made to replicate the original Gameboy Color models, for the iOS emulator GBA4iOS. Gameboy Color and Advance versions available, since they are separate in the app. Not affiliated with the developers of the app.
Open in Safari on iOS device, wait for download to complete, choose "Open in GBA4iOS" and it should then appear in your Skin selection.
Click/tap on the image to download. Second row are the Advance versions.