[Jdot]

That carpet is not rinsed out...at all. You are going to have nasty black dye everywhere if your carpet get even a little wet. That would be like soaking a tshirt in black dye, letting it dry and putting it back on. Wouldn't you want to rinse the shirt out or wash it before putting it back on? If you went your finger and stick it down into that carpet, you finger is going to be stained black...

I tried this last summer. By the time I was done, I had bought 4 packets of powder (RIT), 4 bottles of liquid black (RIT), a bag of white crap that is supposed to help "hold" the color, and two packets of two other brands of black dye I found at craft stores.

Dye does not stick to our carpet. It is mostly made of plastic.

I tried this on my tan carpet as well. It was in much better condition than the OPs and I cleaned it twice before starting. I tried mixing the dye with hot water, salt water, letting it soak overnight, brushing the dye in, and leaving it in the sun. The dye does not stay. My carpet was a horrible shade of purple when I was done. Sure, it look as good that good at first, but if you take a hose with just about any water pressure, it will rinse out. A LOT will rinse out.

I would say it "might" work grey carpet.