Return the accent color menu highlight to Mint-Y.

[alextpedro]

I use Mint-Y-Dark-Aqua and love it, however it's missing the accent color on the selected item in context menus. It opts instead for a more generic light grey.

While for the panel I can just use Mint-L-Dark-Aqua, for applications I enjoy Mint-Y-Dark-Aqua a lot more. The aqua colors used by the two themes are also different enough to cause a little dissonance when mixing them.