Throw Rug Left Stain on Carpet?

I have ivory wall to wall carpet and have placed a red wool multi-colored throw rug from Turkey on it in a dimly lit hallway to brighten it up. Now, I have a fading pinkish stain under the throw rug. I know that I now need a pad or something to keep this from happening again, but how do I get rid of the stain?

By Darlus