The goal is use the color as a reference tool, first by referring to it directly but eventually to see the relationships so clearly that they are stored in your memory as an instant reference for you to access any time you are working with color. Even at night the source of light is most often coming from above. Your mind is comfortable with light being at the top and dark beneath. Yellow is the lightest color on the wheel violet is the darkest.
For this reason, I suggest that you get into the habit of holding the color wheel with yellow always at the top. If you look at the color wheel in the same orientation every time, it becomes easier to remember the positions of each color and how they relate to one another.
