Complement, Contrast, Vibrancy
Complementation is the way we see colors in relationship with other colors. Opposite spectrums tend to be more visually appealing.
Contrast helps direct a user's eye to specific elements on a page. Many suggest to use a very light color for the background and a dark color for the text for contrast and readability.
Vibrancy dictates the emotion of a design.
Brighter colors lead to a different emotion than darker, or muted colors.
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