So this was something I worked on for a while mainly just because I just wanted coloured carts with my coloured Gen 1 and 2 Pokemon injects, however, this does work with the official GBC VC as well. So what's so special about this banner you ask yourself well normally the GBC banner doesn't allow for coloured carts because for some unknown reason Nintendo decided to make the cart grayscale while the GB one is RGB.
Alright, so I recommend you use Kuriimu to replace the images Ohana 3DS doesn't replace all three cart images also because all you are doing is editing the banner.bin I recommend you use ba-GUI-nnertool to extract the banner.bin included in the download and to repack the banner.bin as well. I expect you to know how to extract and rebuilt a CIA file no point explaining how to do that there's plenty of tutorials explaining how to do so.
If all went well you'll have something like this.
[?IMG]� Enjoy!
![[?IMG]](/index.php?title=Special:Upload&wpDestFile=Proxy.php%3Fimage%3Dhttps://i.imgur.com/xeP3LEC.gif%26hash%3D6ae8d190426b7a81fd4d0d2cc686c834){kind=link}