Face transparency attribute

[Sebastian Wålinder]

Hello!

Frames in Emacs recently got the option to set a transparency that makes all 
background colors in the frame transparent to the degree you set.

Is there any way to set the transparency on a particular face? I didn't find 
any way when looking through the documentation.

If not, are there any workarounds and would face local transparency be hard to 
implement?

I'd like to experiment with transparency, making the fringes for instance more 
transparent, as it's not a content area.

Thanks for any help!
Sebastian