Change background colour of NSTextView's default top ruler

By default, if you add a NSTextView to an application and go to Format -> Text -> Show Ruler, a ruler will be shown on top of the text view like in TextEdit with various formatting options, and will look like so:

How would I go about changing the background colour of that ruler? (The ruler should also be there on 10.6, maybe even earlier)

Thanks for any开发者_运维技巧 hints/suggestions!

EDIT ONE: After stabbing around a bit what a call to description on the ruler and what it's subviews are, I came to these results:

Description of ruler: <NSRulerView: 0x10056e580>
        Orientation: horizontal, Rule thickness: 16.0
        Flipped: Yes, frame: {{0.0, 0.0}, {528.0, 55.0}}, bounds: {{0.0, 0.0}, {528.0, 55.0}}
        Accessory frame: {{0.0, 0.0}, {528.0, 24.0}}
Ruler's Subviews: (
    "<NSStopTouchingMeBox: 0x10059b940>"
)

That's a pretty interesting class name, isn't it? =P

I would try to subclass NSRulerView. You could overwrite the drawRect: method and fill the rect with your color.