Even on land, certain wavelengths travel better, and certain colorations are more conspicuous.
Leaf warblers are small arboreal birds with simple songs and various colorations depending upon where they live. Several have their niches in the trees. Whereas some prefer the top canopy, others nestle under shrubs. To optimize visual signaling, birds that live in darker habitats are more brightly colored.
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Colors in plants and animals are produced by pigments and nanostructures. Surprisingly, given the vast diversity of colors in fauna, animals lack many pigment synthesis genes that are common in plants. The evolution and employment of visual signaling through patterning and coloration is not understood.
We lack an appreciation of the developmental processes involved in cellular structures and pattern formation at optical scales. ~ English biologist Innes Cuthill et al in 2017
Given enough light, visual signals provide a vast diversity of possibilities. Like sound, visual signals are readily switched off or on.
Unlike sound, light does not go around corners. But the line-of-sight limitation is not necessarily bad, as it can prevent a predator or rival from catching on.
Patterns and colorations accentuate gestures, but gestures alone are good enough if the intended receiver is receptive.
Male jumping spiders wave their front limbs in species-specific semaphores to females. Fiddler crabs jerk their one enlarged claw in rhythms that other fiddlers comprehend.
Facial expressions are commonly used among mammals. Visual communications may be even more subtle. Among wolves and many ungulates, eyes and/or ears alone convey messages that conspecifics understand.
Visual signals that work over a broad range of frequencies are best for long distances. White contrasted against any dark offset is very conspicuous at every remove – hence the white tails of rabbits and deer, and the dashing eyebrows of mangabey monkeys.