Category II
3 2 1 0
Category I a a0
b b3 b2 b1 b0
c c0
d d0
Based on I and II above, there could be 7 possible combinations for a mutation class, which are colour-coded as shown in the table. This simply gives you how the mutation could be deleterious by looking at the colour - the greender the safer, the redder the badder.
deleterious benign
a0 b3 b2 b1 b0 c0 d0