Yes, BLUISH is a Scrabble word!

Letter values in Scrabble US: B 3, L 1, U 1, I 1, S 1, H 4.

Is it a valid word?

BLUISH is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

of the color intermediate between green and violet; having a color similar to that of a clear unclouded sky