b) Reverse side pigments:
The strains are divided into two groups according to their ability to produce characteristic pigments on the reverse side of the colony, called as distinctive (+) and not distinctive or none (-).A colour with low chroma such as pale yellow, olive or yellowish brown occurs, it is included in the latter group (-).
c) Melanoid Pigments: The grouping is made on the production of melanoid pigments (i.e. greenish brown, brownish black or distinct brown pigment modified by other colours) on the medium. The strains are grouped as melanoid pigment produced (+) and not produced (-) (Shirling and Gottileb, 1966). For the melanoid pigment observation the inoculated plates where kept under incubater for 4 to 5 days. The strains which shows cultures forming a greenish brown to brown to black diffusible pigment or a distinct brown pigment modified by other color are recorded as positive (+) total absence of diffusible pigment, are recorded as negative (-) for melanoid pigment production.