Color is the most important for graphics Designer.
So you want to learn about color theory, do you? Excellent. But where to begin with such a complex subject matter? Color inherently has a very real mental and physical effect on people; thus, it should be used with intention and care. Everything else being equal, color alone can set or change a mood, attract or deflect attention, energize or soothe, or even become the focal point all on its own. The ability to use color conscientiously in your decor will help to bring about wonderful effects no matter your style