If a particle is made of two quarks it is known as a meson. For example, the antimatter counterpart of the electron is the positron. It too is stable and contains the same mass as an electron but has a positive charge instead of a negative one. The stable negative antiproton is composed of antiquarks. A meson is composed of a quark and an antiquark so that the colour requirement is satisfied by the quark being, say, red in which case the antiquark would have to be antired and of opposite charge.
Mesons are short lived, see Table above.