Intuitively it makes a lot of sense. Red is obviously associated with “bad/stop/destructive” and green with “positive/go” while blue is neutral in this respect.

Intuitively it makes a lot of sense. Red is obviously associated with “bad/stop/destructive” and green with “positive/go” while blue is neutral in this respect. The other colors aren’t primary and they have their own problems: orange is too similar to red and yellow is too hard to make out against a white background. Purple is okay which is why it’s used for “visited” links but it’s much less ubiquitous than blue in everyday life which makes it gaudy/distinctive.