I think you can try Jim Dehner's cool method described here:
Please see workbook v10.5 attached in the Forum Thread:
289311teams_v10.3.twbx 68.2 KB
you can write formula for these values and place in color mark.
if sum(total)>500000 then
elsif sum(total)>100000 and sum(total)<500000 then
ONCE YOU place this formula in color then you can select your own colors for these strings.