Name: Rolf Mertig Date: 06/15/12-12:24:19 AM Z
There is no bug here I think.
If you set
SetOptions[SUNSimplify,SUNNToCACF->False]
you get then (switchin on InputForm with FI; ) :
In[14]:= FI; SUNDelta[i,i]//SUNSimplify
Out[14]= -1 + SUNN^2
(* as it should be *)
In[15]:= ?SUNN
SUNN denotes the number of colors.
Trick[SUNDelta[a, a]] yields (SUNN^2 -1).