Percent of Total?

I'm making my first report in Visual Studio 2008 and I cant figure out how to calculate the Percent of Total?  Assuming I have a field in my datatable called Color, I simply want to create a report that counts the occurences of each color and then perform a calculation as to what percent of the total that each of the colors make up.  Basically a report that looks like this....

Color  Count   Percent

Red     50       25%

Blue    100     50%

Green  50      25%

Total    200

I am using a microsoft report (.rdlc).  I have a table that has a header, a grouping row based on Color, and a footer. So using the report expressions, my table looks like this

Color                         Count                                  Percent

=Fields!Color.Value    =Count(Fields!Color.Value)    WHAT EXPRESSION GOES HERE?!?!?!

Thanks!!!

Mike