Custom styles

Hi,

I have bought the full add-ons for Shortcodes Ultimate, including the add-on “Additional Skins”. I am very happy with them, and use them intensively.
But I am not very satisfied with some skins, and I need to change some colors, to adapt with my theme. For instance, “flat-blue” is too “blue” for me.
Is it possible to change/adapt current skins, or to create new skin, by derivation of existing skin ?

Thanks in advance

Sylvain