Given that color is confined, any "long-lived" resonance has to be an $SU(3)$ singlet. Pions are no exception. A pion is effectively a condensation of a left-handed quark and a right-handed antiquark. The color $SU(3)$ is non-chiral, meaning left-handed and right-handed fermions carry the same $SU(3)$ charge, thus the $SU(3)$ charges net out in a quark-antiquark pair. That being said, pions are the bound state of the strong force, thus you can deduce some color-related information by whacking them around.
On the other hand, the electroweak interaction is not confining, thus you could have $SU(2)$ singlets, doublets, or what have ya. Given that left-handed quarks carry weak $SU(2)$ charge and right-hand quarks don't, a pion as a left- and right-handed pair can NOT be an $SU(2)$ singlet.