KMnO4 - potassium permanganate or manganate (VII) is a well-known oxidizing agent.
In acidic conditions purple potassium permanganate is reduced to colorless manganese (II) ions.
If pH is high reduction goes not to to completion as there is not enough H+ ions to remove oxides from the manganate (VII) complex. Reduction goes to form MnO2 precipitate in neutral conditions and green unstable MnO2- (manganate (VI)) solution in alkaline conditions.
The list of ions and complexes containing Mn at different oxidation states:
MnO4- oxidation state +7 purple
MnO42- oxidation state +6 green, disproportionates reduction at pH 14
MnO2 oxidation state +4 brown precipitate reduction at pH 7
Mn2+ oxidation state +2 colorless reduction at pH 1
