If your browser supports colour display, the following patch should be red:
Lower frequencies are called infrared, or far red.
Usage, symbolism, colloquial expressions
In most if not all human languages, "red" is the first color name developed after "black" and "white." Red catches people's attention, and is often seen as a sign of danger: it is thus used for warning signs. The color red is often used to denote anger as in seeing red. The color of blood led red to be associated with the god of war, Mars, and the reddish planet became named for him. The identification of communism as red (since red was the primary color of the flag of the USSR) led to such Cold War phrases as "Red China" (distinguished from Nationalist China or Taiwan) and "the Red Menace."