Does anyone know if you can change the transparancy color in Windowblinds 1.2?

[Tekk]

I want to change the color from a sort of blue transparant color (that changes the background color just a tad so you can tell the window). I want to change it to a darkish red so that the transparant background will go through a red filter you could say. if ya understand what Im saying and ya know the answer then please say!
Thanks