I was reading this, which pointed to this at work. Being partially sighted, I have a CCTV system on my desk. SO, I put something I printed from the colour laser printer underneath and cranked up the magnification.

The system had a hard time finding something to focus on, but eventually would setlle down, and right enough: there are little yellow dots. If I had a UV light, I'm sure they would be much easier to see, but they were viewable.