Color discrepancy between Emacs 22 and Emacs 23

If .emacs contains the following two lines

(set-face-foreground 'modeline "#000000") 
(set-face-background 'modeline "#00FFFF") 

then Emacs 22 correctly uses color #00FFFF (cyan), but Emacs 23 uses a different shade 开发者_如何学Goof blue (#90FBFE).

What is happening?

An image will illustrate the problem, but because I'm a new user here, stackoverflow will not let me save an image. In the meantime, here is the image hosted elsewhere: http://postimage.org/image/1j2ya1ddw/

Version 23 on OS X uses the new Cocoa front-end, and the colors are rendered incorrectly both in that version and in the current dev Emacs. I opened a bug for this last week, having been working on a color theme using precisely-selected colors, and the developers appear to be in the process of accepting the bug's validity.

For me this two lines do their job, but if I set an alpha parameter of a selected frame then colors change similar. I've looked at the emacs 22.3 manual and found nothing about the alpha parameter. But if you look at the 23.3 manual you could find this phrase in the `alpha' parameter section:

It can also have a `nil' value, which tells Emacs not to set the frame opacity (leaving it to the window manager).

Maybe your window manager changes the colors of a frame? If it so this line of code can help you:

 (set-frame-parameter (selected-frame) 'alpha 100)