How can light affect an interior color? For example: what is the effect of natural light on a red wall, blue wall, etc.

Unfortunately your question cannot be answered simply. The lighting has a tremendous effect on material colors, but they are not always predictable without detailed knowledge of the material properties and the lighting. For example one blue paint might still look blue upon a change from daylight to incandescent light and another might become purple. There is also a large variation within a given type of lighting (i.e. different phases of daylight, different types of fluorescent lamps, etc.). Simply put, color science can predict the changes that will be seen, but only when the specific material and light sources have been well defined and/or measured.  more