Yes, that's possible. If you click on the + in front of an expression on the Expression tab of the properties window you will see an item Background Color. If you click on that you can enter an expression in the Definition field. Suppose you have an expression Sum(Sales) and you want negative values to show on a red background. The Background Color expression could be: if(sum(Sales)<0, lightred()). If you want an entire row colored the same then you need to add Background Color expressions (or Text Color expressions) to all the expressions and dimensions in your chart.