You can use the background color attribute for this:
Go to expression tab, open the expression attributes of your bar expression by clicking on the little plus sign next to the expression. Then select the 'Background Color' attribute and enter your condition in the definition field to the right, maybe something like:
=if(sum(Values) > 100, lightred() )
your background color attribute expression must return a color code, either use one of the predefined colors or use rgb() or argb() function to specify RGB colors.
Hope this helps,
I would like to add a similar question: is it possible to change to bar color for an active bar chart and a non-active. What I mean is, I have changed the background and fon color of my objects via variables and expressions. Is it also possible to differentiate between an active bar chart and a non-active?