Why are there no composite particles with fractional charges?

1. Mesons are composed of a quark and an anti-quark, so no fractional charge is possible mathematically.
2. Baryons are composed of three quarks, no anti-quarks mixed in with quarks, so no fractional charge is possible.
3. Pentaquarks are composed of four quarks and one antiquark, charge-wise sum of mesons and baryons so no fractional charge is possible.

Is there some theoretical reason for the lack of composite particles that would result in fractional charges?

For example 2 quarks and one anti-quark could result in a fractional charge, and even it seems that all such combinations would be a fractional charge. Four quark composites would allow fractional charge too if there is not an equal balance of quarks and anti-quarks. It has to be possible to detect, so if no actual fractional charges been observed then there must be some theory to explain this. Is this the reason for the theory behind color charge and color confinement?

It is very interesting if there is no fractional charge observed at all across all known particles – composite particle or not.