The tauon neutrino has never been directly detected, but scientists believe that it exists based on the effects it has during experiments. Quarks The second type of fundamental fermion is the quark. Like leptons, there are six flavors, or varieties, of quarks in three generations. The first generation quarks are the up and down quark. They, like the first generation leptons, are the most commonly found because they combine to form neutrons and protons.
All quarks also color charge of either red, blue, or green.
These are not actual colors, but are the way scientists describe the way the quarks interact through the strong nuclear force. The strong nuclear force acts to bind quarks together into composite particles called hadrons. A hadron can be either a fermion, if it has an odd number of quarks, or a boson, if it has an even number. The most basic fermion hadrons have three more quarks than antiquarks and are called baryons. Protons and neutrons are baryons made up of up and down quarks.