When I vote using the Android app, the button highlights briefly in orange as expected and then returns to the normal black (so both vote buttons are the same color). I expected the highlighting to remain in place to show my vote.
The post score reflects my vote, and if I tap the vote button again it cancels my vote (and updates the score again). So my vote is there; it's just not shown. If I vote, navigate back to the list of questions, and then return to the page where I voted, my vote shows in orange and is persistent. Votes I've previously cast show up and are persistent on first view; it's only new ones that behave like this.
By its nature, it's hard to take a meaningful screenshot.
I don't use the app a lot, so I don't know how new this is. My phone says I'm up to date (1.0.77).
