Created attachment 385545 [details]
Test case revealing the problem.
Attached test case illustrates that at least one method has not been implemented in the SVGStylable interface: getPresentationAttribute 
This test case also covers:
- getting the rgbColor property from the SVGColor object 
- getting the red/green/blue properties from an RGBColor object 
- getting the float value from the CSSPrimitiveValue object 
Opera and WebKit both pass this test case.
It would also be nice to add this (and any other) unimplemented DOM methods/properties to http://www.mozilla.org/projects/svg/status.html
This is what the code says within that method...
// Let's not implement this just yet. The CSSValue interface has been
// deprecated by the CSS WG.
Oh the things I'm learning...
Well since it's been 6 years and there's no new version of that document, and Opera and Webkit have implemented this interface, maybe Mozilla needs to go with the other browsers?
The other option is to implement the SVGT1.2 uDOM: http://www.w3.org/TR/SVGMobile12/svgudomidl.html so that we can use getRGBColorPresentationTrait()?
We don't support SVGColor in every situation at WebKit and consider removing this interface completely in the future since it is deprecated. The same for getPresentationAttribute() and SVGPaint.
See webkit bugs:
This method is deprecated in SVG 1.1.