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.

(Which I don't think is right as it fails the grammatical test, but interested in audience reaction)

Seeing red, sky blue pink, etc:
I'm going to give the baton to INJ. But perhaps Projoy should have it. The word on the card is simply "red." I got hung up on the philosophical distinction between the color itself as a physical phenomenon and the name that we give to the color. I ended up giving a misleading answer on PJ's "name of a color" question. Apologies all around -- I'm new to this. I should have watched longer before accepting any batons.

Fair enough, and I think outside of the name of a color q you answered the questions pretty fairly (altho I think I might have been entitled to at least a few claps from the audience for "red shift", tho!).

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[PJ] Agree, I was not so good at channeling the audience, either. :-)
*offers compensatory applause and the baton* Do you want the baton, then? Or is it INJ's?