There is a phenomena that occurs beneath area rugs that lay on installed carpet. At least three factors contribute. 1) The fibres of installed carpets are typically glued to the backing. The glues offgass and this causes a shift in the PH balance of the carpet, which over the course of 4 or 5 months often develops a yellow tinge in the carpet beneath the area rug. When this happens, it is usually irreversible. 2) The light usually comes in the windows and dulls the carpet surrounding the area rug. When the area rug is pulled back, you then have a nice bright rectangle where the area rug was (95% of the time). 3) Dyes from area rugs are often unstable and bleed into the carpet underneath, especially along the edge of the area rug. By and large, in my experience (and I have alot of experience), when you put an area rug on a carpet, it is a one way trip. After about 4 or 5 months, you are going to be committed. My recommendation is that if you want to spend some money and add color to the room, get some new custom drapes.