In contrast to the transparency an luminosity of yellow, red is relatively dense and solid. It can be moved a long way towards orange or violet and still be seen as a essentially the same colour.At the far end of its bluish range, it produces a variety of exotic hues, including magenta and purple.

Even when adulterated towards russet or when darkened it remain recognizable. While yellow can be felt to radiant light, red radiates the most energy.