Palettes of 4 similar-hue colours were rated as more pleasant (harmonious) than dissimilar-colour palettes.
Sanocki & Sulman (2011)

Lakoff and Johnson (1999) saw that there are many proverbs and sayings that have to do with form characteristics and emotions. Parallel / equal movement / oneness: togetherness, concomitant, positive, appropriate, power, strong, suitable, assisted, helped. Perpendicular / disunity: wrong, not combining, opposing, less strong, hindering.