Contraste des couleurs complémentaires
Complimentary colors can make a strong balance to ease viewer’s eyes, if they have been applied on particular ratio. This is ‘Rule: Contrast of complementary Colors’, one of six contrast rules devised by Harald Mante in “La Couleur en Photographie.”
Purple and yellow are compliments, according to Mante’s book, with 9 and 3 units of luminance in sequence. So the frame must include purple area 3 times more than yellow. This is how it get into balance and may comfort the eyes.