If you notice red, blue, yellow and/or pink on the ears or nails of the pups it is used as a marking so that I can keep the pups separate and know which pup is pup. I put it on theirs because Mom wants to keep licking it off the nails and putting bands on their necks the Mom will tear them off. As the pups get older I may be able to tell them apart better but as they are younger you may notice the markings on them.