When he experimented with the relationship between adjacent colors, showed that the human eye can be deceived by color

Colors that lie next to one another on the color wheel and share qualities of hue as a result of the mixture of adjacent hues, harmonious hues.

 "In visual perception, a color is almost never seen as it really is — as it physically is. This fact makes color the most relative medium in art."-John Cage 

1. 6 i think i don't know for sure tho