Melanin boosting is a kind of artificial tan.
Sometimes one might prefer an uneven, selective tan, creating a stencil effect of overlapping multiple shades in rectilinear patterns, outlining and highlighting musculature. This must be the Parisian fashion.
Cath had a melanin-boosted tan, but not one of the Paris jobs.
In order to hide his Sprawl pallor, and not having a time for melanin boosting, Case was applied artificial color with a marker.