Temperature is one of the 4 characteristics of color; the others being: Hue (or local color), Intensity (its brightness), and Value (the dark or light of a color).
As we look at the color wheel the yellow, orange, red colors are the warm range and the green, blue, violet colors are considered the cool range. Within each color, however, is a warm and cool version.
For example - RED is considered a warm color but the tube color Alizarin Crimson is a cool version of red, especially when compared with Cadmium Red Light, which is a warm (and quite orange) red. Both are in the RED family, but Alizarin is the cooler and more violet red, while Cad Red Light gives us a warmer version in the same family.
When painting with Alizarin in the landscape or in a still life, try highlighting it with Cad Red Light, thus adding depth to the work and more interest by not only changing color value but changing color temperature.