Usage patterns
地味な〈物〉a plain, understated (color, design, outfit, etc.)
She always wears clothes in subdued colors.
地味な性格a quiet, unassuming personality
He has a reserved personality and doesn't stand out much.
地味に〈動詞〉to (do something) more than you'd expect; quietly (do something)
This task actually takes surprisingly long.
地味に〈形容詞〉surprisingly, more ... than expected
That dish is surprisingly spicy.