We just painted my daughter's room turquoise :) I'm from the mid-Atlantic region of the US and I pronounce it /ˈtɜrˌkwɔɪz/ . http://www.macmillandictionary.com/us/pronunciation/american/turquoise

The ladies already gave you great answers. I wanted to point that it's clearly pronounced like this in the States and we're not sure about the UK. The word is obviously French, they pronounce it "terk-waz" and that means "Turkish". I just happen to know that the color is named after a mineral (or whatever it is) of the same color, which you can commonly see as a gem used in handmade jewerly.

Personally I would probably describe turquoise as bluish green. I think that opinion can change based on a persons experience. Someone who has studied art or fashion may be more exact in determining which color is which. I am from mid-North America and I pronounce it "tur-koi-ss". koi like koi fish.