Red, blue, yellow etc. are not just colors. These are emotions, feelings, memories, reflections, associations. They play a very important role of sings or symbols. Seeing a color or thinking about color produces a certain reactions in our mind....
Those are the first words that I read in the ColorAssociations.pdf. The document describes a study on associations that are perceived from colors written (in English) by Olga Dmitrieva. The study unfortunatelly covers only associations for red color. But any way this information could be useful when a photographer wants to convey a certain message in a photograph and uses red color for it.

More studies on colors you can find here.