I'm not an expert in this field, however... Maybe it should be clearer if I say that the initial and final states of a scattering process must be color neutral; during the scattering process the quarks can mix up, as the are confined pratically in the same place. Then they can split, to the final states, only in color-neutral "groups".
And that's why you happen to see only color-neutral particles. Can you understand now? (If you don't, probably is due to my lack of knowledge in this field ;-) )