Apply a color or opacity to whole group

[slightly99]

I'm using a group of stencils to create an office floor plan. The stencils create black objects, and I'd like to change them to a light grey so I can overlay them with black text and make it readable.

Each stencil is just a group of objects - is there an easy way to apply either a grey color or a lower opacity to the group?

I'm using v.3 right now - I do have a license for v.4 on another machine, so can use that if need be.

Thanks

matt