I agree with the above comments, stain identification is lot more to do with common sense than science. Consider the room (lounge, bedroom etc) the family (children, pets etc). If it's a red sticky stain in a childs bedroom it's probably Calpol, if there are black sticky spots in the lounge and there's a toddler in the house it's probably squash or juice. In a dining room most spots are likely to be protein stains, if there's a pet in the house and the stain is yellow it's probably urine and so on.
Nobby