Anurag Kashyap has called Ugly his darkest movie.
The greys are, indeed, dark enough to be ugly and painted with precise brushstrokes to make the art stay on your mind long after you have witnessed it.
The dark can't be seen into. It makes one blind, curious, or scared; sometimes all at once.
All protagonists in Ugly are blinded... by ego, rage, greed, lust, envy... mostly a composite of these to various degrees. Yet they're reaching for a common end, each in a uniquely twisted manner.
Whether they get there or destroy each other on the way is a thought that floats on till the narrative winds-up, after a series of acts that affect you... very much!
With the actors performing their best, smooth frames, and a background score that complements the story; Ugly is Beautiful.
Is a movie 'good' if it entertains you? Ugly won't. It will leave you disturbed. It may make you want to revisit your priorities.