It certainly can be!
Myself I'm using plexi. I taped the circumference of my monitor with (painter's)tape and covered the monitor square with plain paper, making sure no paint would get on that piece of the plexi.
I found some leftover cans of black spray paint (one gloss and one semi-gloss) and emptied them on the back side of the plexi in thin layers. Did about a layer or 6. I ran out of paint, but it looked more then decent from the outside.
However, there will be a lot of light on the inside of the cab, so I tested if the paint was dense enough. I held a flashlight directly behind the plexi and looked at it from the other side. There was still a smudge of light visible, so I used some leftover pieces of vinyl (the very thin, self adhesive stuff) to put on top of the paint to make sure no light at all passes through.
On the outside, you just see the "smoked" effect of the paint shining through the plexi. Done deal, no light comes through

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