Probably the changes are because we keep experimenting, seeing new things, and grow too. Sometimes I swap my characters' palette or reimagine them in a different situation (e.g. what if he took his grandma more? What if they switched hair texture) and sometimes the results are decent or good enough to make me want to make a change.
Yes, I don't know if comic artists will more likely to retcon the color change. Maybe with novels, we don't re-describe the characters every so often so the first description gonna stuck more, whereas in comics you see the characters all the time so the change can look more gradual.
