In your eye there are cones that pick up red, green, yellow and blue light. This light is then transmitted to your colour opponent ganglion cells. Some are excited by red and inhibited by green; some the other way around. Some are excited by blue and inhibited by yellow; others vice versa. Phew! Everyone's brain is different. If you have a preponderance of ganglia that are excited by red, then red might appear more exciting to you than green. Or perhaps you have more yellow-excited than blue-excited ganglia - in that case blue might appear calming to you.