The opposite of "more muted" is "louder," "brighter," or "vibrant." "Muted" refers to a soft or subdued quality, so antonyms would be words that suggest a more expressive and lively quality. For instance, think of a bright and bold painting versus a muted and subdued one. To describe the first, you might use words such as vivid, rich, or bold. But, to describe the latter, you would use words such as subtle, understated, or subdued. When looking for antonyms for "more muted," think of words that describe something as lively, colorful, or eye-catching to create a strong contrast with the original meaning.