This hack looks awesome. very excited for it to be released and try it out on a flash cart.
The colors look great, I am in no way advocating that they change but one thing I never read mentioned is the original LCDs used in GBC systems. They were quite a bit more "dull" than modern screens, and as such many games went with the oversaturated colors so they would pop more on the original reflective GBC screen.
If i recall, they even made some later games, like the zelda oracle series, have two color palettes. One Palette for when used on a GBC, one for when played on a GBA, because the colors on one screen didn't look right on the other.
With a modern emulator on a nice backlit modern screen, I think the more "pastel" colors you're going with will look more accurate, it's just that people are used to the oversaturated colors of other games.
Can't wait to play "For the Frog the Bell Tolls DX"! Keep up the awesome work.
Out of curiosity, any idea how much larger than the original the colorized ROM would be?