Yes, SCARLET is a Scrabble word!

Letter values in Scrabble US: S 1, C 3, A 1, R 1, L 1, E 1, T 1.

Is it a valid word?

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

of a color at the end of the color spectrum (next to orange); resembling the color of blood or cherries or tomatoes or rubies

Also: orange red, blood-red, cherry-red, ruby-red.