CF is one of the Casimir operator eigenvalues of SU(N)SU(N)SU(N) (CF = N2−12N\frac{N^2-1}{2N}2NN2−1).
CF
Overview, CA, SUNSimplify.
CFC_FCF
SUNSimplify[CF, SUNNToCACF -> False]
N2−12N\frac{N^2-1}{2 N}2NN2−1
SUNN
NNN
SUNSimplify[SUNN^2 - 1, SUNNToCACF -> True]
2CACF2 C_A C_F2CACF