A resource request. Do you have any good examples of color used in a mathematical research paper?
One example I've seen is here, in reference to tensor categories: https://arxiv.org/pdf/1612.02762.pdf
EDIT: Another example from the same author: https://arxiv.org/pdf/2003.02124.pdf
Other examples are of knot tricolorability and graph colorability (I'm sure there are loads).
To be specific, I'm asking for papers where you think the colors were useful: either added something meaningful to the paper, or else simply made it easier to follow.
(Most of these will probably be recent papers, since my impression is old-fashioned journals were generally black-and-white)
PS: This question is inspired by the following (closed) question: Resources for using color in mathematical exposition