Colour perspective - whites and reds appear to advance into the foreground, and the voilet recedes into the background giving a sence of spacial depth.
Hamonious colour - like relatives, these share the same family eg red and orange. Side by side on the colour wheel they operate harmoniously with each other.
Psychological response to colour - colour creates a sensation in the brain. Our first reaction is emotional and is linked with the personality of the viewer, sometimes in a sub-concious way.