Board Thread:The Quarters - Q & A/@comment-24548070-20140215075807/@comment-24489486-20140222232635

Habits are created yellow; clicking - moves them towards red, + towards blue, but left to themselves, over time, they tend back to yellow. You'll never see a blue to-do - they are created yellow and move towards red. Ticking off items on a to-do checklist has no effect on colour value.

There was some talk in the tavern about this the other day - IIRC Megan wassaying she got stressed with having red to-dos, and wondered if at some point we'd be able to choose colour values (say a range of blue -> purple for to-dos). But as far as I'm aware, it's not possible at the moment.