Change fill color from Python

[Magnus Henoch <mange freemail hu>]

I want to change the fill color of an object from a Python function.
I try the following in the Python console, where obj is an object:

color = dia.DiaColor(1.0, 0.0, 0.0)
TypeError: cannot create 'DiaColor' instances

color = obj.properties["fill_colour"].value      # works

obj.properties["fill_colour"].value = color
TypeError: 'DiaProperty' object has only read-only attributes (assign to .value)

Are these things (creating DiaColor objects, and changing properties)
not implemented yet, or am I just missing something?

Magnus