Why might my 11 month old daughter's teeth be turning yellow?

Plaque : Primary teeth can collect plaque just like adult teeth , take a wash cloth , put a corner over your finger and gently wash/brush the yellow teeth.

Plaque or: It could be plaque build up and it can be related to diet, but given the age i would think of plaque first. All teeth no matter the age need to be brushed and cleaned daily. Your child should also be seen by a dentist at age 1 for first eval.