Venn diagram - shading/highlighting overlapping parts

[loopa1]

Hi all

I've created a venn diagram in Powerpoint just by overlapping circles and changing the transparency of each object, however, I now have the need to highlight certain segments of the venn diagram.

Because I've got around eight or so overlapping circles, some of the segments are now quite small and some are shaped quite weird.

Is there anyway I can apply a border, or somehow "pick out" these individual segments so when I deliver my presentation it's immediately apparent which part of the diagram I'm talking about?

Many thanks.