'Dark matter' is a term coined by scientists. You may need to visit some research universities to ask them why they named it that way. I don't think glass is considered to be dark matter - it is not invisible even though it is transparent.
I guess if you knew that an alien was standing in front of you, you could spray-paint him. But how would you know?
Well, spray paint is not the only way to detect things not visible.
You may accidentally walk into the 'dark matter alien'.
Why do you think that visiting a university is better than seeing what they
have to say by their articles on the www?
I have studied dark matter quite a bit, and the only proof of its existence
is simply that they had a statistical theory that suggested that a certain
amount of light in the universe represented a certain amount of matter.
Then, because of gravitational lensing, they realized that there was more
matter than their statistics had previously suggested. So this extra matter
was called 'dark matter' because it was not associated with emitted light.
Beyond that, I'm afraid it is just normal matter.
I cannot read wiki articles because they mostly have been written by people
with obsessive-compulsive-disorder.