Colour psychology

Warm reds and oranges read as urgent, blues read as calm and technical, black reads as serious. The association is real and weak. It shifts by culture, by subject and by what everyone else in the feed happens to be doing that week. On a thumbnail, legibility beats mood every time: the image is small, often on a bright screen, and sitting in a column of competitors. Pick colours that separate your subject from the background and from the thumbnails around you, then adjust for tone. Consistency does more measurable work than any single hue.