Yes, ruby is a Scrabble word!

Adjective

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

Noun

1. A transparent piece of ruby that has been cut and polished and is valued as a precious gem

2. A transparent deep red variety of corundum; used as a gemstone and in lasers

3. A deep and vivid red color