"To use colour effectively, you need to know that it cheats most of the time."
According to the interaction with the background, the colour can vary either in the direction of light, then be perceived brighter or darker, or in the direction of the intensity, so be perceived warmer or colder.
Just because it is relative and difficult to trap and to judge, I always found interesting the colour theory of Joahannes Itten, who tried to make less relevant the colour, less subjective and more objective. According to some people the colour cannot be outlined, it is like a good music as a background of an image, which is essential to convey the emotion. But even music has its rules.
Itten's theory, as I have always seen using it in my illustrations, lets us free to use any colour combination we would like to use as the same time giving us a deeper knowledge on the use of colour.