Percentage bars are ugly

[Alan Pope 🍺🐧🐱 🦄]

The percentage bars showing progress are orange background with a white centre and black text.

* The black text is unreadable on orange
* The white centre of the scroll bar looks strange, like the progress bar has had the middle hollowed out

To reproduce

Open software properties
Toggle the Source code option in the first tab
Press close button
At next dialog, choose reload
Expand twisty to show details of the software update.

See screenshot

I'd expect the text to be readable white on solid orange or black on solid white.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: software-properties-gtk 0.96.20
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Apr 28 12:28:50 2016
InstallationDate: Installed on 2016-04-27 (0 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PackageArchitecture: all
SourcePackage: software-properties
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.