Open rhythmbox.
Press the shuffle or repeat buttons.
It's impossible to tell whether they're on or off as their state doesn't change.
See the two attached screenshots. One has shuffle enabled, one doesn't. It's impossible (for me) to tell which is which.
ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: rhythmbox 3.2.1-1ubuntu1
ProcVersionSignature: Ubuntu 3.19.0-16.16-generic 3.19.3
Uname: Linux 3.19.0-16-generic x86_64
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Mon May 11 12:00:03 2015
InstallationDate: Installed on 2014-06-16 (329 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
SourcePackage: rhythmbox
UpgradeStatus: Upgraded to wily on 2015-05-09 (1 days ago)
The buttons do appear depressed, but is barely visible, and has been an accessibility problem for me too.
It seems that the buttons are impossible to tell apart except for their orange border when hovered, and when not hovering, the button's inset effect does change, but it's still hard to tell apart when put alongside other buttons.
I think it can be best fixed by darkening the orange outline when a depressed button is in focus. Other methods like depressing the button more would in my opinion make the design more inconsistent, as from what I can tell by the way the buttons were made.