Howdy, I'm Furry Girl, the webmaster and one of the models on EroticRed.com. There's a lot of fake period porn out there, which is ridiculous on levels other than just the straight-up humor factor. For one, a good fourth or fifth of all women are menstruating at any given time, so it can't be that menstruators are such a unique group (like squirters) that their pussy functions need to be faked due to a lack of availability and a high demand. It's also head-scratching because fakes featuring jam, food coloring, and BBQ sauce look nothing like real menstrual fluid. Maybe the lowbrow fetish sites are just too lazy to bother scheduling their models to get real red content, or figure that their customers are such oddballs that they wouldn't know the difference, but either way, it's insulting to all flow-lovers and period-positive types. Since an injury to one is an injury to all, I've taken up the noble cause of putting together a comparison of fake and real "menstrual blood", using tampons. Click on photos to enlarge.

First, there's the issue of uniformity. Real menstrual fluid (on the left) in composed of vaginal secretions, blood, and bits of tissue from the lining of the uterus, mistakenly called "clots" by many, although menstrual fluid does not clot. A fake tampon (on the right) is straight up bright red, and stains that which touches it.
I've actually seen poorly faked tampon-based beverages in the past, so I thought I'd make a couple of martinis for our little comparison.
If you drop a real tampon in a toilet or mix it with any other liquids, it retains much of its contents and bits of uterine lining, only changing the water to a dusty pink if you squeeze it out or let it sit.
The fakes, on the other hand, leak bright red onto everything quickly.
Even after being rinsed and rung out, the hero of our story, the real used tampon, retains most of its lady-bits and color patterns, and the faker is just pink.