I should say you should check to see if it doesn't stain/run the colours of something in a patch that most people don't see first and to remove the bulk of what's staining it first. That said, I've used it to good results in an old flat with light tan carpet upon which I had dripped coffee, a dark blue carpet in the kitchen which was stained with a bunch of things (yuck kitchen carpets, almost as bad as toilet carpets), a knitted jacket of my sister's which was stained with a stain the dry cleaners claimed they couldn't remove, and one of Mr A's suit jackets.
Another tip: squeegee and dry your shower/tiles around your tub after a shower or bath and you won't need to scrub mould off the grout often.
Which reminds me, we need a new squeegee.