visable wevelengths are from 480nm-700nm

the colors we see objects as are the reflected color in most cases (all others are absrbed)

the sky appears blue due to refraction light comming through the astmosphere refracts off the molucules the angle durning the day produces the "blue" appearence changing to red-orange in the mournings / evenings as the sun is at a different angle.

theres also the "uncommon" green flash that has a specal case making it less seen.

my two cents as a student of OPTICS