The color wheel primary colors are vital when building sites as it can give you a competitive advantage among other websites. The secondary color wheel has to do with the colors coming from the combination of the primary ones.
Red, Blue, and Yellow are the so-called primary colors. The primary color wheel is the one that has all the colors that make the others.
Part 2: Why should you know about primary/secondary color wheel as a designer?.Part 1: Definition: What is the primary/secondary color wheel?.