How much wood would two woodchucks chuck if they agreed they both would chuck wood?

Born from tears of the sky and sun's laughter, I paint arches in the air, a fleeting bridge of colors you can't walk on. Catch me if you dare, but I'll vanish like a dream upon waking.

I wax often, despite no threat of hair. I also become blue, though that is rare.

What’s rosy, golden or green on the outside, snowy and sweet on the inside, and hosts a star at its core?

I'm always in you, sometimes on you, but if I surround you, I can kill you.