The seeing of bands of color is actually more about the human retina and cones. As such the cones are more sensitive to particular wavelengths of electromagnetic energy (for brevity we call these RGB, the perception of yellow is the RG both being stimulated) and less sensitive to other wavelengths. At this level it does not involve the brain/language as implied by this post. Obviously categorizing and naming colors is the brain activity; as is the opponent process, but that's not particularly relevant to the retinal activity that "creates" the bands.