I've noticed that there is no option in Xfce settings to configure color which fades out after clicking Logout in menu.
With a little help of IRC guys I've found that this color isn't to be configured by Xfce user. I've found a file that makes that color constant: xfce4-session-4.6.1/xfce4-session/xfsm-fadeout.c. Then I made a little experiment which proved I've found correct variable: changed 32nd line of the file to this: #define COLOR "#000000", then recompiled my xfce4-session package. Now fadeout is nicely dark and does not flash into my eyes, when I want to shut down or log out from my dark themed Xfce session.

My question is: why not make this settings configurable to the user?