At the Sony booth they were demonstrating an effect where one color is selected (like a bridesmaids red dress) and some type of 'filter' is used... then only that color is shown - everything else is black and white.

I downloaded a trial version of Vegas5 - What is this effect called and how do I do this effect?

It was pretty simple when it was demonstrated BUT I can't remember how it was done. Any help would be appreciated.

Thanks in advance.