When you consider neutral colors, muted shades are part of it. Most people who are into neutrals ie whites, tans and black, don’t think that colorful muted shades are neutrals. They lean more to the whites than they would to pastels.
Muted colors are the opposite of bright and vivid colors. They are made of subtle shades like soft lilacs, butter yellow, powder/pale blue. In case you are wondering, any color can be muted by being dulled or greyed. No matter how bright a color is, once you mix it with grey, they become muted.