Datatable Column Integers and Strings

I have a Datatable that is similar to:

Colors       7y        8y        9y       10y     Total

blue           1          1         2          2          6

green        0           3        1           0         4

Total          1          4         3           2        10

%             10%    40%    30%     20%    100%

I have created the columns to be string for Colors and int32 for the rest, so that I can use the expression in Total column to get the row totals and then .compute(sum(col)) for the column totals.  This proposes a problem when I want to insert the percent values with a percent sign for aesthetic reasons.  Is there anyway I can either compute strings, I have seen to use convert inside the sum from older posts but that does not seem to work anymore, or insert % into an integer field?

JR