Are you trying to make them 3 dimensional like your Protools buttons?
If so, then hopefully you created your button icons using a "toolbar_blank.png" file and alls you would need to do is copy your toolbar_blank.png image file to the Default's resource image folder or if you're trying to bring the default toolbar buttons into your theme, then you just need to copy those toolbar buttons into your theme image folder which should have a toolbar_blank.png file in it.
Here, I just put a 3D toolbar_blank.png image file into the Default's resource folder. The default buttons now are 3D.
Now if you're saying you're trying to make them grey like yours, then there's one of 2 ways to go about that. 1. Change the color of "Main Window/Transport Background" which is the 1st item in the tweaker list 2. Add the color to your toolbar_blank.png image file.