I also found the color scheme to be difficult to understand. A friend suggested interpolating between red and green depending on how close you are to the correct key. This is not too hard, since red is (255, 0, 0) and green is (0, 255, 0), so you can compute a distance (normalized to [0, 1]) and output (255 x d, 255 x (1-d), 0) to get the interpolated color.
Hey, I just released a new update that adds multiple color schemes to help with colorblindness! At some point I may add a color blind mode that does away with the need for colors altogether, but for now this should make things a bit better. Also, there is now a gauge next to the board so you can more easily see the range of colors (unfortunately, it doesn't yet work on Firefox).
Check it out!
I also skipped forward a day, so if you already played today you can play again with the next word to try it out.
Ah, the other color schemes look really good (especially I like the heatmap one). However, the default stoplight one is nearly impossible for me to disambiguate. For example, in [1], I can't tell which of mine are closer at all (I don't think I am colorblind, but maybe I'm just in for a surprise today).
Anyway, overall, a very fun variant. Thanks for sharing!