The speaker starts out unimpressed. Pink sweatpants and turquoise nails sound like a clash, and the speaker admits they never liked either one. The first two lines are blunt and almost grumpy, as if the speaker is setting down a long-held opinion.
Then the third line turns everything around. Once "you" put these colours together, the speaker's view changes completely. What looked wrong on its own now works as a whole. The person becomes "a colour bomb, a rainbow," something bright and a little explosive, moving "perfectly through the room."
The last comparison, to "minimalist art," is a playful surprise. Minimalism is usually quiet and plain, while this outfit is loud, so the phrase seems to suggest that the person's confidence makes the loud look deliberate and clean. The mood is warm, amused, and admiring. The speaker seems to feel both affection and a bit of awe, and the poem suggests that the person, not the clothes, is what makes it all work.