Bluesky: No
Starshine: No
I have observed by reading past rounds that others do this -- so I will summarize some of the more interesting information your questions have revealed:
It can be expressed as one word.
It can be used as a noun. I will add that it can also be used as an adjective.
It is visible.
Light is involved.
You might learn about it in physics class.
It is sometimes related to some art.
A ten year old gets it -- I will add that I know two year olds who get it too.
"The name of a color" is an element of the abstract concept but not the thing itself. I will add that it is not the name of something -- but of course it has a name.
My shouted reply could be construed as a clue.

Dysthymia: No.