"God," mutters the off-screen cameraman, Miles. "That is nasty."
Footage of the rug in question begins about 2:30in, after a basic Ikea rug is cleaned to show what color the cleaning run-off usually is. This makes unambigiously clear what the yellowing component of the detergent froth is, drooling and coughing from the cleaning machine as it heaves back and forth over the rug from hell. Jump to 5:50 for the stomach-churning denoument as a giant hand squeegee is used to force out the remaining juices.
P.S. The heavy-duty vacuum cleaner they use in the video is the Hoover Commercial [Amazon], which I heartily recommend. Mine replaced an ancient Sebo model that had to be prized (cold and dead) from my living hands. It's not as good as the (now $700!) Sebo was 20 years ago—and I hazard that it won't last quite as long—but it's far better than the dainty junk typically recommended by the usual suspects.