Treemap legend?

All,

I'm struggling with how to extract the colors assigned to data in treemaps.
I thought that the would be part of the 'node' object, but I don't see
them there...

Any pointers on the best way to generate a legend for a treemap?

Thx.

Chris.

PS - I'm relatively new to JavaScript, so there's a non-zero chance I'm
just missing something obvious.