Purple rags - cleaning cloths?

[Brightdays]

I ordered some purple rags but I already have a stack of washcloths we use for most of the kitchen cleaning. Can anyone explain how or what they use the purple rags for? We really only use paper towels for cleaning grease or dog messes. Sometimes I wonder about all the extra time with laundry and folding but we are all used to grabbing a "rag" for clean ups.

Sorry for this really silly question.