I use the coloring in the sixth tab "Visualization". There you can choose the column with the actual sales and could use the above or under field. One problem there is the = in both choices.
Otherwise you could expand the + before the expression. There you find background and textcolours. There you can add an expression like
if(Sum(actualSales) < Sum(forecastedSales), Red(135), Green(135))
Then the background or the number is red or green. So you can easy define more than two cases.
I hope, it helps a little bit.