Here i imported the Windows & Caption Buttons > Aero > DWM Window > Frames > Window > Left image from 8 into 8.1 and set PADDEDBORDERWIDTH to 0 and unchecked "Show shadows under windows" and I don't see any color:
Or if you just mean the added color then forget about importing anything, keep PADDEDBORDERWIDTH at zero and uncheck "Show shadows under windows" at Control Panel\All Control Panel Items\System\Advanced system settings\Performance.
Don't forget that now your top and bottom frame images will be at Windows & Caption Buttons > Aero > DWM Window > Frames > Shadowless Window > Normal > Bottom and Top