This issue was discovered as part of fixing RT-36445. When I modify modena.css to use a darker style and then running HelloMenu, I can see that initially the submenu arrows and check marks render with white, and then turn black when when hovered, as expected. However, after bringing up the menu again (and having hovered over the menu items), I can see that the arrows and check marks have turned black. See attached screenshots.

Here's the CSS to add in to the .root of modena.css:

-fx-base: #3f474f;
-fx-accent: #e7eff7 ;
-fx-default-button: #7f878f ;
-fx-focus-color: #efefef;
-fx-faint-focus-color: #efefef22;