Shiva Purana classifies rudraksha by Color and the number of faces (vaktra) possessed by them. In the former, they are white (Sveta), red (Straight), yellow (pita) and black (Krishna). these corresponding to the four Varna, Brahmins, Kshatriyas, vaisyas and sudr respectively and is to be worn accordingly (Vidyesvara Samhita 25, 12, 11, 44).
Agni Purana parts rudraksha in four classes. They are Siva, Sikh, Jyoti and Savitra. And further breakdown of the four varieties In each of these are also listed.
The second type of class if blues, proposed by the Siva Purana, is dependent on number of faces found in rudraksha. both Siva Purana (Vidyesvara Samhita) and Padma Purana allocate money even to each of these 14 varieties. So as per the purans there are 14 classes of rudraksha. Classes of rudraksha can be from different view of color or use also. Classes of rudraksha can be based on the society work groups like brahmins etc.