Color schemes work best when the amounts of the colors used in the design are not equal. A variety of proportions creates more interest, and you can set the mood and energy level of a design or illustration simply by which colars you use as dominants and which play an emphatic or accenting role.
If you create a design using 1/3 red, 1/3 yellow and 1/3 orange, you limit your ability to use color to create emphasis or focal point. Also, the color scheme can become discordant and lose its appeal or miscommunicate. IT can also be perceived as static, even if the colors are warm in temperature and fully-saturated, as in the example below.
To create interest using 3 colors, try a 1/2:1/4:1/4 [50:25:25] ratio. This give the larger proportion dominance, and allows the smaller amounts to serve as accents.
If your design uses 4 colors, one rule of thumb is to assign 1/3 of the design space to one color, making it the dominant, and then break up the remaining two-thirds of the design into smaller, unequal areas: 1/3:1/6:1/6. The color that is used least can become the accent if it is lighter or darker enough in relation to the other colors.
In the above diagram, notice how much more engaging the color scheme on the far right is compared to the scheme on the far left.
Use color to support the purpose of the design.
There are no set rules for distributing color throughout a design. Your decisions about color should be based on what you are trying to achieve with the design and who you are trying to reach. Design is not art. It is not creative expression. Design communicates. Purpose and audience should drive all of your color decisions.
One method for learning how to use color effectively in your designs is to observe how others have used it. Look at any visual design or illustration that intends to communicate, attract or engage a user. What is the message? What colors are used to communicate the message? What hue families and color qualities were chosen? Are the colors mostly light? Intense? Dark? Are they warm or cool? Are they subdued or neutralized? Are the differences among colors subtle or obvious? A little awareness of how color is used in your everyday activities can help instruct you. Keep your eyes open.