Creating a style that changes the default control colors

I've been tasked with changing the default color scheme of two WPF UI components in our application:

1. All scroll bars in the application have to use a grey color palette. The up\down buttons, slider button and background colors have to be changed through a style template.

2. All combo box drop down buttons must use the same gray color.

I've Googled in earnest, but I can't seem to find the magic template spell that makes happen. Is there an easy way to do this, or do I have to pull out Blend?

Thank,

Aaron