[NTG-context] Margins around figures

Deat ConTeXt users, I am making a presentation with ConTeXt, with numerous MetaPost figures. Now, the only problem is that my white MetaPost figures don't blend well with the dark background of the screen. This isn't too good since the text labels in my figure's edges appear too close to the edge. What I'd like to know is, whether there's a way to specify some extra margin space around the figure, which would provide some more white area around the MetaPost figure. Alternately, is there an elegant MetaPost way of specifying figure margins? Oh, and my MetaPost files are in separate .mp files; I include them after converting. Thanks! Kumar -- Kumar Appaiah, 458, Jamuna Hostel, Indian Institute of Technology Madras, Chennai - 600 036