Possible products from anion analyses
Under acidic conditions, a blue colour is observed. This results from the formation of N,N'-diphenylbenzidine. In the course of the reaction, diphenylamine is oxidized to a quinoid radical which subsequently adds to another molecule of diphenylamine. 
Under slightly acidic conditions, bleaching of the solution is observed. Sulfite is oxidized to sulfate while $\ce{MnO4-}$ is reduced to $\ce{Mn^{2+}}$.