Looks like this is an issue with @2x (retina). The background of MenuPane in Ace is a 1x1 image (why?! its color is #F7F7F7, is it being auto-extracted from a resource somewhere upstream?). In the gem abbot, that is working fine, but in latest master it's upscaled @2x to a 1x2 image, where the top pixel is the correct color and the bottom pixel is the horrible pink color. Something's gone wrong here, I assume it's in Abbot (or in one of its dependencies), and it may impact other areas.
My fix is going to be to override Ace and define the menu's background as a color. Just a color. No 1x1 pixels. But does anyone know what's up with Abbot's apparent behavior change?
Cheers,
Dave