I have never put this on the site, but I have a scan of Columbo's real, TV ID from the "new" (1980-present) series, smuggled out of Universal by an inside source.
I especially like the horrible ID photo -- it shows that, even though nobody expected (even in 1980) that viewers would get such a close look at the ID, somebody was witty enough to give Columbo a classically awful-looking ID photo, like the worst drivers-license picture ever taken. Columbo looks like he just dragged himself in from a 3-night stakeout, and on top of that, as you say, they gave it really bad coloration.
The ID cards might not be official canon on issues like Columbo's name, but clearly somebody is having great fun with the props.
OK, I know this has been overdiscussed and that people are sick of it. But I just accidentally tripped into this thread while searching for something else and wanted to add some thoughts for the record:
(1) If Columbo's first name were Frank, I would be happy with that. It fits.
(2) I understand and appreciate the point that the show's creators, writers, and Falk himself never gave Columbo a first name and wanted to keep it unknown, and so the ID card was not intended to establish a name. I agree with that logic, except...
(3) You can also argue that intended by the writers or not, the fact remains that the ID card *is there* in the episode. We can speculate all day as to who intended what and whether that was a prop guy's decision and whether the director should have vetoed it if no name was intended to be established...but at the end of the day all we have to go by is what is actually there in the episodes themselves. It doesn't matter what the painter intended to paint or not to paint--all that matters is what ended up on the canvas. So rogue prop-guy or not, a name did get established in an episode. I can certainly see the point that there is no higher authority on "Columbo canon" than the actual content of the episodes, as that *is* Columbo.
(4) I picked up on the Harry thing in Columbo Goes to the Guillotine, too. When the episode first aired on TV (and I was much younger), I felt *certain* they were dropping a hint that Columbo's own name was Harry. He seemed to deliver the line with a (metaphorical) wink. But upon rewatching it now, it doesn't seem as dramatic as I remembered. Cass points out tht it might well be an in-joke, but as a reference to Falk's other non-Columbo work.