I believe that color is taken from the Button Face color & is a Windows setting that can't be separately changed by WB. In other words, whatever the Button Face color is, that's the color the unfocused highlight will be. Same is true for Outlook & some other apps that use an unfocused highlight. You can change the Button Face color in the Classic Colors section of SkinStudio, but it may have some funky effects in apps that are either unskinned or only partially skinned, especially MSOffice apps.
