Right click on the top slanted border line with the coloring tool. When the coloring box pops up, use the space bar to get the left hand color box highlighted by the white box. Then select transparent in the upper right corner. This is in 7.0 format. What version are you using??
Start with a Simple numeric or Simple string indicator in the Classic controls palette.
Select both FG and BG colors as Transparent and then color the indicator.