today one customer called, that Rhino 6 (in Rhino 5 this works) doesn’t export colors anymore, when he exports IGES (with default settings). All objects are white now in his other CAD-system, called Pictures by PC (an ACIS-modeller from Germany).
As far as I can tell, there have been no significant changes to IGES export for V6. But it does seem that the default for the “Use render color” option has changed. I don’t know why. I’ll ask around.