Git Gui on OSX Mojave Dark Flashes on Repaints

On the newest version of Git available via Homebrew (2.19.1), when the
gui tool needs to repaint the screen (refresh a file, change a focused
file, stage files) the window that is repainted flashes a dark gray
before returning to white. This was not occurring on High Sierra
yesterday, but has occurred today. I believe it was occurring on an
older version of Git as well, but I updated to ensure that it wasn't
something that was already solved (it was not).

I can provide more diagnostic data if needed. Thanks!

Matt