I'm color blind -- not extremely, but not mildly. Red/green/brown are difficult for me to see. While reading the wiki the other day, I saw that on the research pane there are different color outlines to indicate whether a node is fully upgraded (green?) or not (yellow?).

After zooming way in on the tree, I can see the difference, but it's impossible to tell from even a medium zoom. Changing this would be awesome, thanks! The rest of the game (I think? though who knows what I could be missing!) looks great.

Added an option to the Settings screen (1.9 Beta) for a better color accessibility.
If anyone have spotted any other places where colors are hard to distinguish, please report them in the comments.
Note: already fixed the research nodes colors, rarity colors (Rare) and Special blueprint graphics