I thought bunt was a neutral term that simply means colorful or multicolored. One German-speaking friend recently told me that bunt was not neutral at all and often carried a judgement. For example, ein buntes Kleid can be positive and complimentary, whereas ein buntes Bild is mildly pejorative and describes a riot of colors out of harmony with each other.
My dictionary translates bunt as gaudy, motley, ragtag which would be highly insulting in English when applied to someone's clothing.
What are the precise rules for using bunt?