There's actually 5 skins! If you sign in you can also set your preferred skin in preferences. Check them out below:

https://en.wikipedia.org/wiki/Wikipedia:Skin?useskin=vector

https://en.wikipedia.org/wiki/Wikipedia:Skin?useskin=vector-...

https://en.wikipedia.org/wiki/Wikipedia:Skin?useskin=monoboo...

https://en.wikipedia.org/wiki/Wikipedia:Skin?useskin=timeles...

https://en.wikipedia.org/wiki/Wikipedia:Skin?useskin=minerva

Not the gp: I have redirector with a regex url rewriter that gets me the skin on all wiki pages. (it is somewhat complex, due to anchors and such) Writing this comment so that I can find it again later so I can post it here, if yoou want to have it.