Rangbaaz is an Urdu word which, with its commonness, permeated through languages and can be heard even in Bangla now.
Rang is color, and -baaz is a suffix that is used for someone doing something particular, for someone who is an expert at that particular thing. So literally it would be 'an expert at colors', but the word doesn't take the literal meaning of colors, but takes a figurative meaning, such that rangbaaz is someone who changes colors, colors of his personality in a way. So Rangbaaz in a sense is used for someone cunning, someone expert at changing his moods, ways or his complete demeanor.