The navigation buttons (back and forward) in the software center do not match those in nautilus. Nautilus uses grey, whereas the software center uses orange. Both applications use the dark toolbar. In my opinion, the grey looks better with the dark toolbars (Firefox uses a light toolbar and orange looks fine), but whatever the final decision, they should probably be the same.
ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: software-center 13.10-0ubuntu1
ProcVersionSignature: Ubuntu 3.11.0-11.17-generic 3.11.3
Uname: Linux 3.11.0-11-generic x86_64
ApportVersion: 2.12.5-0ubuntu2
Architecture: amd64
Date: Sat Oct 12 18:28:26 2013
InstallationDate: Installed on 2013-06-23 (111 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130621)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: software-center
UpgradeStatus: No upgrade log present (probably fresh install)
Not an issue with Humanity icon theme.
Nautilus developers decided to use monochrome symbolic icons for the navigation, while other apps use the regular color icons.
Both the icons are available for use.
The Ubuntu project just needs to decide what the standard should be for apps and then apps just need to follow the project's standard.