P-phenylenediamine can be purified by dissolving in water to which activated charcoal is added. The resultant solution was boiled, filtered and allowed to cool.
Usually the colour of the product is white but may be darker when its oxidized by air.
The following book can be very useful too.
Perrin, D.D.; Annarego, W.L.F.; Perrin, D.R. 'Purification of Laboratory Chemicals', 2nd Edn. Pergamon Press, New York, 1980.