Final answer:
Color is the most vivid element of art and design, offering a complexity that can influence mood and themes in artwork.
Step-by-step explanation:
The most vivid element of art and design is color. This element stands out because it encompasses a vast array of combinations and variations, making it complex and deeply influential in artistic expression. Humans have unique responses to different color combinations, which artists manipulate to direct the viewer's attention and convey specific moods, themes, or messages within their work. The elements of art, such as line, mass, shape, and value, all play significant roles, but it is color that often captures and holds the viewer's gaze with its potential for depth and emotion.