Face for window separator

[cothrige]

I have my mode-line foreground set to red ,(set-face-foreground
'mode-line "red"), in my .emacs, and this has made reading what is
going on in the Console a bit easier for me.  However, I will
occasionally split a window vertically, C-x 3, and then things are
less clear.  The separator which is between the left and right window
is white on black, rather than red on black, which makes it blend
in with the window contents.  I would like to set this to match my
mode-line, but have been unable to find any way to do this.  Perhaps
there is a particular face used for this which I can tweak, as I did
mode-line?

I greatly appreciate any suggestions.

Patrick