Hello,

To change the background color, you will need to generate the default style with Microsoft Expression Blend.

1. Right click your xaml page and open in Expression Blend.
2. Right click UXGridView>>Edit Additional Template>> Edit RowStyle.
3. The default style should be generated automatically. Then save the xaml.
4. Back to Visual Studio. In Resources>> Visual State , you can see all the state such as normal selected, mouse over, etc.
As you can see, they are using Background Rectangle. Then, try to find Rectangle with Background Rectangle name,  you should able to change the color in the gradient.

Regards,
Handy