We have performed optically detected spin coherent transient measureme
nts for two distinct localized triplet states in brown colored diamond
. The triplet states of interest belong to the N-V center in its groun
d state and the V-O (or 2.818 eV) center in its photo-excited phosphor
escent state, respectively. In this paper we focus on the dynamics of
cross-relaxation processes which occur when small magnetic fields are
applied in such a way that the defect triplet states of the probed cen
ters are tuned in resonance with other defects in the lattice of diffe
rent spin temperature. The coherent transients reveal the dynamics of
cross-relaxation and pure dephasing processes. A quantitative analysis
shows that the observed cross-relaxation arises from magnetic dipolar
interactions between the probed defects and randomly distributed othe
r defects in the lattice.