The checkgmail icon background is set to whatever colour is selected in:
System > Preferences > Theme (tab) > Customize Theme (button) > Colours (tab) > Windows:Background.
For me, selecting a background colour in checkgmail Preferences doesn't work - the colour is always the same as Windows:Background
Interestingly, though, WiCd wireless manager doesn't seem to be affected by the same problem, even though its icon is also in the Notification Area panel.
The checkgmail icon background is set to whatever colour is selected in:
System > Preferences > Theme (tab) > Customize Theme (button) > Colours (tab) > Windows:Background.
For me, selecting a background colour in checkgmail Preferences doesn't work - the colour is always the same as Windows:Background
Interestingly, though, WiCd wireless manager doesn't seem to be affected by the same problem, even though its icon is also in the Notification Area panel.