noun, any of a group of colours, such as that of a ripe tomato or fresh blood, that lie at one end of the visible spectrum, next to orange, and are perceived by the eye when light in the approximate wavelength range 740--620 nanometres falls on the retina. Red is the complementary colour of cyan and forms a set of primary colours with blue and green. Related adjs rubicund, ruddy

From Collins

©HarperCollins 2008. Collins English Dictionary definition of red