SSRS Tip : Matrix Report - Format/Style SubTotal fields

I had a matrix with column and row subtotals. I wanted to differentiate the SubTotal Row/data with a different Color. If I select the "Total" cell or the the subtotal row/column it will only format the Total labels, not the subtotaled data. The Cells of the Subtotaled data will also not be visible.

I struggled a bit and then found the solution:

In the "Total" textbox, there is a Green triangle. Right-click that triangle and see the Property of "Subtotal". This is where the Style(s) of SubTotal should be set.