Colors of collapsed margins

Does CSS2 define the color of collapsed margins where there are more
than two margins that have collapsed?  If it doesn't, should it?

These situations involve layered block level elements, for example
"<DIV> <UL> ... </UL> </DIV> <DIV> <UL> ... </UL> </DIV>".  In these
situations, it is possible that each margin does not have the same
color, since the DIV may have a background color different from that of
DIV's parent.  This can create some rather ugly situations.  ( See
http://www.fas.harvard.edu/~dbaron/csstest/listbox.html in Opera or
NGLayout -- MSIE has some bugs so the problem doesn't appear.)

David