The search progressively filters your papers as you keep typing. We only include results that match on all the search terms, so your "color pink" papers would also have to have the word "Floyd" in the title, abstract, etc. in order to be included in a search for "Pink Floyd".
That said, you cannot search for a specific ordering of words, so you would receive all results which include those two words. One of our main goals with search in Paperpile is to have it be very fast and one result of this is that we do not have advanced search features such as phrases and Boolean operators.
You can restrict searches by first selecting a folder, label, and/or filter. This is the best approach if you find that the size of your library is affecting the accuracy of your search results.