There are other particles made of quarks (generally called hadrons). Those with and odd number of quarks are called baryons. Mesons are those that have an equal

There are other particles made of quarks (generally called hadrons). Those with and odd number of quarks are called baryons. Mesons are those that have an equal number of quarks and anti-quarks. "All" protons we see are the same because the exotic configurations decay. (While protons are not yet known to decay.)