Spills often resemble explosions. They are generally larger in diameter near the backing than on the surface. Tracking commonly leaves a clearly defined shape like a handprint or footprint. Tracking stains are usually limited to the tips of the tufts. Where tracks come from could indicate the cause.
Different chemicals react differently to different colors and dyestuffs.
As we have noted, they also react differently under various climatic conditions. In general, red spots on tan or beige carpet may suggest strong acids. Yellow stains indicate reactions caused by strong oxidizers or bleaches. Green or blue stains may indicate sunlight combined with a catalyst. In general, once a textile product has been chemically stained, there is little that can be done by the individual to restore the material to its original color and condition.