Someone had brought up to me the idea of creating an overlay with a bezel in every color fo the rainbow, but because I'm extra, I took it a step further and made a slightly fancier variation.
Included in this repository are both grid overlay and non-grid overlay with a bezel in each of the following colors:
Red Orange Yellow Green Blue Indigo Violet
Additionally, these come in a Gameboy Advance SP and a Gameboy micro variant.
Grid
No Grid
Grid
No Grid
NOTE: You can put these wherever you want, so long as you are able to easily navigate to them within retroarch's settings and so long as they're not with any sensitive files that are crucial to retroarch or your Anbernic device. Otherwise, it may be best to use my recommended defaults locations.
Move the OtterBot folder to mmc > MUOS > retorach > overlays
Open a GBA game, then the Quick Menu, and go back to the main menu. Then go to Settings > Video > Scaling.
Integer Scale: Off
Aspect Ratio: Custom
Custom Aspect Ratio (X Position): 0
Custom Aspect Ratio (Y Position): 0
Custom Aspect Ratio (Width): 640
Custom Aspect Ratio (Height): 426
Bilinear Filtering: OFF
Crop Overscan: ON
While playing a game, open the quick menu and go to On-Screen Overlay > Overlay Preset.
Select Parent Directory until you get to the directory that contains the folder named OtterBot. Then go to OtterBot > gba > Prismachrome and pick the overlay you'd prefer.
Go back to the Quick Menu and then go to Overrides.
If you want the selected bezel for all GBA games, select Save Content Directory Overrides.
If you want the selected bezel for just the current GBA game, select Save Game Overrides.