What is the nature of color?

It seems to me that colors are not objective, but rather a feature of consciousness. I can see red, you can see red, but I can't know that you see red the way that I do. It appears that colors are perceived, not objective. This makes me think that animals perceive colors differently, cats can't see red, etc. But if color is not objective, what is it that differentiates blue from red light? Are those wavelengths of light simply placebo effects on our consciousness? Is color related to different frequencies in different ways, like light versus sound? Is there some objective measure of color that I am missing?