I definitely understand where you’re coming from with the desire for a more unified color palette, but it’s tricky because there’s a lot of compounds, environmental variables, and other bars that all need to be visually distinct from each other (otherwise, something like hydrogen sulfide might be the same color as ATP, which I believe would be ultimately more confusing), while also having meaningful colors in many cases. For instance, hydrogen sulfide’s yellow-green color references the color of sulfur, which also sets it apart from ATP and nitrogen. Furthermore any blue compounds will have to be distinct from oxygen and CO2, and any red compounds will have to be distinct from oxytoxy-NT and the player’s HP bar.
Definitely agree with starting a better style guide though! I’ve been stressing out too much about stuff that’s way out of my area of expertise and it’s been a while since I’ve thought about anything actually graphics-related