Windows 7: Invisible colour for msstyles

Hey, I was trying to replace the markee for the progress bar (resource number 664 under IMAGE in .msstyles) and I keep getting a black backgound even though it is translucent in the png. My question then is, what is the translucentcolour value for 7?

If it's done the same way as it is on the taskbar then the transparent parts shouldn't be 100% transparent, but really really close to full trans.
Try for example giving the parts you want to be transparent a level of 99% transparency.

See this old thread to see if it makes more sense than my above explanation!: skinning question - taskbar transparency

Cheers, that makes sense, I'll try it when I get some time.

Thanks