Why do the colors red and blue look trippy when placed side by side???

Answer 1

Light transferred from those colors to the retina stimulates different cone cells. Whenever a continuous stimulation is placed on the retina, image fatigue sets in (as when you stare at a bright light and then look away and "see" a dark spot). The same happens with colors, and the fatigue color is the compliment. So, when red and blue are adjacent, retinal fatigue makes the border look as though it is multicolored and shifting.