One group of words which indicate colour are adjectives only and have no noun uses. They indicate that something has a colour that is similar to another colour, usually one of the basic colours.
A scorpion, with a kind of luminous greenish glow to its back, was seen retreating into a sand slit soon after I had risen from my camp bed.
He had several days of stubble on his chin and his teeth were yellowy stumps.
The words in this group often combine with colour words. Pinky is only used in this way, and bluey is usually used in this way.
blackish bluey bluish brownish greenish greeny greyish orangey peachy pinkish pinky purplish reddish whitish yellowish yellowy
The Mooloolah River was a beautiful bluish-green.
They proved to be Brown Fulvettas, which are fairly nondescript little grey, brown and greyish-white birds.
She highlighted Juliana's cheekbones with a pinky brown blusher.