colors in MPgraphic

[Hans van der Meer <hansm@science.uva.nl>]

In MPgrapic I do want my own colors for drawing lines etc.
These are set up in plain.mf's ("_op_" and "background").
In \startMPinclusions I just do that in order to get the drawing  
color I want.
But then \startMPgraphic appears to reset colors (both "_op_" and  
"background" I suspect).
Can this be changed? In plain.mf there is already a setup, so there  
seems no reason for \startMPgraphic to interfere.
It would be nice if the color setup done in \startMPinclusions would  
be honored.
It is a nuisance to have them set up in a special initalization file  
and then being forced to repeat this at the start of every graphic.

Question: what tinkering with metapost parameters is done in  
\startMPgraphic exactly? (I could not find out readily from the  
ConTeXt sources)
Which of these can be removed without danger for its operation,  
leaving settings in \startMPinclusions unchanged -- and will that be  
done?

yours sincerely,
dr. H. van der Meer