So I was reading about EM waves and radiation. My textbook says that frequency of light depends on the temperature of a body. As the frequency rise up, the color shifts from red to blue. For example, copper. This is supposedly true.

I have this weird doubt - if copper changes its color with temperature, how do crayons have different colors? Crayons are made of same material and have a constant temperature. In fact how do any of the objects emit different colors, all being at same temperature.

I do not know if I am missing a basic crux about this argument. I would really like to know. Thanks in advance! :)