mtb:
it's my fault. I started using gifs years ago to grab the screens and it's too late now to change it all.
Also, the goal of the screenshots is not to replicate and store the original graphics, but only to give an idea of what the game is like. So, for us, it's not necessary to have all the colours exactly right.
Konrad:
The full details weren't entered for Great Giana Sisters, so your search didn't come up. I've fixed it now... The database is still being worked on, BTW