The Blue Ambiance Theme is a modified version of the default Ubuntu 15.04 Ambiance Theme. As far as I am aware this is the first and only known to be working colored theme for Ubuntu 15.04. And as the title suggests the progress bar, highlights, folders, and open and close buttons have all been replaced by blue variations. It is a subtle change but more pleasing to the eye than the default theme.
Extract as root to /usr/share/
Use Unity Tweak Tool to select Ambiance Blue Theme and Blue Icons
Please let me know if you have any trouble with the theme.
I modified the widget icons and css.
The folder icons are from the Elementary icons.
The open and close buttons are from Ravefinity\'s Ambiance Colors Aqua Theme.