You can't change the color of a rectangle through XML.
It can be done by scripting, or by hand...
Ok great. Can you tell me how i chang it with script.
I am building al flex application that sends a request to a indesign Server and he makes the pdf form the template.
myRectangle.fillColor = mySwatch;
For more details check out the InDesign CS Object Model.
I haven't done this, but I believe it is true that you can:
1. Add an attribute to your xml tag that identifies the fill color you want to use.
2. Use an XMLrule to call a script to interrogate the attribute and apply the color.