In finding a truffle the right trees must be present and the red signifies that the truffle was found near an oak. Truffles are formed by fungi that are partners with certain trees. You will not find truffles under maples, for instance, because maples do not form ectomycorrhizae, a form of symbiotic relationship that occurs between a fungi and the roots of various plant species Ttrees. You can find truffles under oaks, hazel nuts, hickories, birches, beeches, and other species.