@WillS
Thanks, WillS. Dyeing is ideal for nylon, wool, and silk. Viscose can be dyed, but it's really a junk fiber as you have accurately indicated. Unfortunately interior designers love viscose because it feels soft and looks nice, but it's pretty dang hard to work on if it has a staining issue.
Here's an example of a viscose rug that was destroyed by a rug washing company in Chicago. They put the rug into their centrifuge with another rug while it was still wet. This caused dye bleeding and severe browning. The rug washer was on the hook for this $5,500.00 rug that they had damaged and wanted us to restore it back to the original color. I explained to them that this wasn't possible, that the only option would be to dye the rug to a darker color (brown or gray). The customer didn't want this done so they abandoned the rug and had to purchase a new one for the customer. I dyed the rug to a medium brown and was able to sell it for $3,500.00