  Galaxy clusters, which underwent a recent ($\leq3$ Gyr) major merger, offer a
harsher environment due to the global hydrodynamical disturbance and the
merger-shock heated ICM. However, the aftermath of such extreme cluster
interactions on the member galaxy properties is not very well constrained. We
explore the integrated star formation properties of galaxies through galaxy
colours, as well as morphology buildup in three nearby ($0.04<z<0.07$) young
($\sim$0.6-1 Gyr) post-merger clusters -- A3667, A3376 and A168 -- and 7
relaxed clusters, to disentangle merger-induced post-processing signatures from
the expected effects due to high-density cluster environments. Exploiting the
optical spectroscopy and photometry from the OmegaWINGS survey, we find that
post-merger clusters are evolved systems demonstrating uniform spiral
fractions, uniform fraction of blue galaxies and constant scatter in the
colour-magnitude relations, a regularity that is absent in dynamically relaxed
clusters. While no clear merger-induced signatures were revealed in the global
colours of galaxies, we conclude that different global star formation histories
of dynamically relaxed clusters lead to considerable scatter in galaxy
properties, resulting in the pre-merger cluster environment to potentially
contaminate any merger-induced signal in galaxy properties. We discover red
spirals to be common to both post-merger and relaxed clusters while post-merger
clusters appear to host a non-negligible population of blue early-type
galaxies. We propose that while such merging cluster systems absorb extra
cosmic web populations hitherto not part of the original merging subclusters, a
$\sim$ 1 Gyr timescale is possibly insufficient to result in changes in global
colours and morphologies of galaxies.
