While consulting the Sonic 2 documents provided by Tom Payne, I realized that the palette called “COLOR2” is not exactly a copy of the Emerald Hill one, as it might seem at first glance.
The order in which the palette lines are presented is:
- Backgrounds 1
- Backgrounds 2
- Sonic and Tails
So, taking the values that were printed on the sheet and inserting them into a Sonic 2 ROM dump, I converted this:
I then restored the missing colors (Sonic’s blue tones and the colors used for the water cycle):
And when I loaded the game into an emulator… The colors more or less fit Emerald Hill, although some of the final level assets must have used different colors back then, or maybe didn’t even exist.
The final colors look like this:
But wait, doesn’t that bright water in “COLOR2” remind you more of Green Hill? If we directly compare the three palettes:
So we can conclude that we are presented with a color palette halfway between that of Green Hill (Sonic 1) and Emerald Hill (Sonic 2).
As a final note, it is curious that for a palette so early in the game’s development, according to the sheet on which it was printed, Sonic’s blue colors were already considered “non-fixed” like those of the water cycle and appear as unusable values “FFFF”. This could indicate that they already had the idea of implementing Super Sonic from practically the beginning of development!