Dye Methods:
Solution Dyed - In a solution died carpet the process begins with melting down the polymer into a solution and then dying the entire solution. Next, the solution is astride into the Nylon. This process is similar to a carrot, if you slice it open you see orange through and through. It is orange on the inside and the outside. If you get a stain on a solution dyed product you're able to aggressively clean it out, even a bleaching process will take out the stain and leave the color as good as new.
Yarn Dyed - In a yarn died carpet the process begins by melting down the polymer and astruding it in its natural color, which is clear white. Then the yarn is taken and put in a vat of dye where it is died. This finished product can be compared to a radish. It is red on the outside, but white on the inside. The carpet will have the dye on the exterior of the yarn. In some cases you have to be careful with aggressively cleaning it. If you clean too aggressively you might remove the stain as well as the dye, leaving the white interior of the carpet exposed.