I am using Win 10, thanks for the respose.

Quoting LightStar,

reply 3

OK, thanks to DaveBax for pointing something out to me. In Windows 7 that image only does borders around the popup window, and the color of the rest of the area is controlled by the button colour text setting in SKS 10. In Windows 10 the full image is used for the popup background. So evidently the skin you are using has that color of an image, or there is no Non captioned Window Edge image assigned at all.

If you cannot fix the issue yourself, you could try contacting the skin author and see if they could fix it. 

You make absolutely no sense.  The OP asked about changing the color of the taskbar (one of the defaults in WindowBlinds) and I would like an answer also.

Maybe we should be asking;

When you select modify style

What exactly do all of the selections refer to?  I mean if should be easy to select something like 'taskbar' change color, change transparency.

Made me curious and had to play... fwiw on Win10 if there is no image defined in "Non captioned window edge" it looks like the color used is System Color / ButtonDkShadow (which can also be changed in WBConfig/Modify Style/Change system colors).

Dave, yes that controls the color. But it can also control many other areas especially some border colors.

As far as the non captioned window edge image. Not sure what WB you are checking or using that it doesn't have an image. Most everyone I know uses an image in that location. In win 7 it does nothing so maybe that is why some skins don't have it in there. I have always used an image in there along with many others. 

IN win 10 the image will control that menu. It does help to in most cases match the skin better. One reason is most of the time you would want the ButtonDkShadow color dark and it doesn't match many skins. 

Try one of my skins, Lightstars, Don's, who ever that use the non captioned image. Again which most of us all use. Check the menu then remove the image and apply. Now you will see the color.

The reason I didn't mention the color location in the thread is because as I said most have an image in there. So changing the color you will not see any change. As far as the skin you say doesn't have that image I don't know what it is. I see only a couple made mt Stardock Design. So what skin are you using?