What is the likely implication of the consistent bright green coloration across the wide West African range of D. viridis?

It suggests either a relatively recent divergence or strong stabilizing selection pressures related to camouflage effectiveness

The maintenance of a uniform, bright green hue across the extensive geographic range of the Western Green Mamba suggests specific, consistent environmental demands are at play. One possibility is that the species has undergone a relatively recent divergence event, meaning there hasn't been enough time for significant color mutations to become established across subspecies. Alternatively, it points toward powerful stabilizing selection pressures. This means that across the varied, yet consistently dense and sun-dappled West African canopy environments, the bright green offers the optimal camouflage, and deviations from this color incur a significant survival penalty.