lor mixing effects.)
In general, all dull cool colors are warmer than their saturation hue match, and all dull warm colors are cooler than their saturated hue match. Thus, burnt sienna is cooler than cadmium scarlet, because it is less saturated (closer to gray).
The same principle applies if you are using the alternative yellow/blue violet contrast: ultramarine blue is made grayer (and warmer) by the addition of some burnt sienna, and burnt sienna is made cooler by adding some cobalt blue.
warm/cool contrast effects
Now we can address the third question raised above: what explains the visual or design effects created by warm or cool colors? In color theory writings the two most commonly described effects are:
warm colors "advance" in an image that is, they seem to stand out or attract attention, or seem spatially closer to the viewer, while cool colors "recede" or seem to melt into the background: they have a depth effect.
warm colors are active, arousing or cheerful, while cool colors are passive, restful or subdued: they have a mood effect.
Visual Associations. color theory typically explains these effects through absurd color associations "ice is blue, and so blue seems cool," or (my favorite), "a distant mountain appears blue, so blue seems to recede from us."
These fictions completely fail to explain the visual effects, because there are numerous and obvious counterexamples. For example, in landscapes the blue sky above us appears much closer than the whitish horizon, so why doesn't blue advance or white recede? If a sunset appears behind those blue mountains in the evening, why doesn't red appear to recede more than blue? On a hot summer's day a noon blue sky radiates far more heat than the reddish sunset, so why isn't blue warm and red cool? Why don't we say "snow is white, so white seems cold"? Or why is red warmer than white, if white hot is much hotter than red hot? It's astonishing that color theory writers have repeated these nursery rhymes, generation after generation, without any regard for the facts.
Indeed, thoughtful artists rejected this color theory nonsense almost from the beginning. Here for example is John Ruskin, writing in 1862 about the depth effect:
It is a favourite dogma among modern writers on colour that 'warm colors' (reds and yellows) 'approach,' or express nearness, and 'cold colours' (blue and grey) 'retire' or express distance. So far is this from being the case, that no expression of distance in the world is so great as that of the gold and orange in twilight sky. Colours, as such, are ABSOLUTELY inexpressive respecting distance. It is their quality (as depth, delicacy, etc.) which expresses distance, not their tint [hue].
An Optical Illusion. Undeterred by Ruskin's critique, Joy Turner Luke offers an explanation for the depth effect that has become popular recently: warm colors are "advancing" because their focal length is longer than cool hues, which is the cause of chromatic aberration.
All hues cannot be perfectly focused at the same time. The eye focuses slightly differently on long wavelengths (reds) than on short wavelengths (blues). The lens becomes slightly fatter and more curved to focus on red in comparison to when it is focusing on a blue or green. ... When the eye focuses on nearby objects it makes a similar, but larger, change than it does when focusing on red; ... the muscles that control the lens are most relaxed when we gaze off into space. This small difference in focus may account for the fact that blue and green seem more relaxing and to recede slightly in space.
This explanation doesn't work for three reasons. First and most important, our eyes are adapted in many ways to eliminate chromatic aberration from visual experience. Depth perception is critical to primate survival, and objects that "advance" or blur because of their surface color would destroy that acuity. We simply never see aberration effects, unless they are produced by cheap artificial optics. The focusing of our eyes, the appearance of objects and our color associations cannot be influenced by optic