To make sure that they get along, use skinks of a similar size and species. Enclosures can have several females, but males will tend to compete with one another. As a result it's best to give new skinks a trial run to see if they get along with the other skinks before moving them in permanently.
The difference is that a skylight filter is a basic colour correction filter with a slight magenta tint which has a similar effect on skies as a UV filter (which cuts out part of the spectrum), which is neutral coloured.
(See dichroism for the etymology of the term.). Dichroic filters can filter light from a white light source to produce light that is perceived by humans to be highly saturated (intense) in color. Although costly, such filters are popular in architectural and theatrical applications.