Discoloration or color loss along baseboards suggests insecticides. In the living or dining room where houseplants are kept, it could be leakage from pots containing plant food or from plant sprays. Stains around the base of furniture could be contamination from furniture polish. The important thing is to isolate the cause of the spot and take whatever steps are necessary to prevent future exposure. The pattern of the stain indicates how it happened.
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.