How to change status bar on iMac using 'Leo Color Bar'

LeoColorBar

As penguinrob suggests, you could set the menubar to translucent, andinfluence its color by changing the color of the part of the wallpaper underneath the menubar. LeoColorBar, pictured below, basically automates that for you.

Despite the fact that it hasn't been updated in a while, it's worked perfectly for me in Lion.

A black menu bar

Alternatively, there are applications likeNocturne that you can use to set your menu bar to dark gray.

MenuBarFilter is another application based on Nocturne that turns your menu bar black.

The latter two applications, however, didn't work very well for me in Lion (especially in full-screen mode), so your best bet would be to stick with LeoColorBar.