Denote which stylesheet is currently selected by Highlighting or creating a checkmark by it.

[Tor020]

Part of StyleSheet Switching Interface Project

[PresleyWong]

How about considering to remove currently selected stylesheet from drop-down list?

[Tor020]

That sounds alright as long as you can still see the style thats currently selected in the main box, like this

[PresleyWong]

#72 remove selected stylesheet from drop-down list

[Tor020]

Updated for 2018 hacktoberfest