"The dark dress" isn't that common of a thing to say in english either, no?At least not if we are not talking about physical appearance (dark hair, dark eyes, dark skin etc.) Instead, greeks usually say

Tο σκουρόχρωμο φόρεμα - The dark-colored dress (when they don't specify the color) and

Το σκούρο πράσινο φόρεμα - The dark green dress (when they do specify the color).

I hope I helped. ^.^

Yes. ^.^

Yes, it's not a Greek word ;)