  Merging of galaxy clusters are some of the most energetic events in the
Universe, and they provide a unique environment to study galaxy evolution. We
use a sample of 84 merging and relaxed SPT galaxy clusters candidates, observed
with the Dark Energy Camera in the $0.11<z<0.88$ redshift range, to build
colour-magnitude diagrams to characterize the impact of cluster mergers on the
galaxy population. We divided the sample between relaxed and disturbed, and in
two redshifts bin at $z = 0.55$. When comparing the high-z to low-z clusters we
find the high-z sample is richer in blue galaxies, independently of the cluster
dynamical state. In the high-z bin we find that disturbed clusters exhibit a
larger scatter in the Red Sequence, with wider distribution and an excess of
bluer galaxies compared to relaxed clusters, while in the low-z bin we find a
complete agreement between the relaxed and disturbed clusters. Our results
support the scenario in which massive cluster halos at $z<0.55$ galaxies are
quenched as satellites of another structure, i.e. outside the cluster, while at
$z \geq 0.55$ the quenching is dominated by in-situ processes.
