We all have an inbuilt knowledge of color. These are colors that we are familiar with.
Most people can tell if the color white is contaminated with an excess of an unwanted color.
The same applies to other memory colors. We all understand that the sky is blue we also know that at late evening and early morning the sky will have yellow, orange, and red. We also have a clear knowledge of the sky in the area in which we live. For example, the sky in Los Angeles may never be close to the color of the sky in Hawaii. An area that is white with printable detail.