You're probably right - it may not be travertine at all.
I saw some tesserae being lacquered in France a few years back and I was astonished at how the clear lacquer totally changed the shade of the original tile. In fact, they looked very much like the photograph you've posted.
I Googled Red Travertine myself last night and was surprised how much the images differed from each other. Yes, there were some that looked like marble, but I couldn't seem to find two that looked the same. It's clearly very confusing.
Anyhow, I wish you the best of luck with your quest!