We're working through the Griffith's introduction to elementary particle physics and are wondering about the quark antiquark annihilation process. There are actually three first order processes, but my question is about the two feynman diagrams I sketched in paint.
If we look at a QED annihilation process, like $e^-$ and $e^+$ we get two photons. The diagrams eventually look the same, if you replace the gluon lines with photon lines. I understand, that we can not differentiate the two photons, that's why we have to draw both diagrams. However, the gluons have different color charge, so I'd say I can differentiate them and therefore they are not interchangeable, thus I only get the left diagram.
Can someone shed some light on this?