I haven't found a really good way to do conditional
formatting on an element. The hacky way I handle it is to use two
of the same element boxes, with one on top of the other. You go
ahead and change the font colors so that one of them is red and the
other green. Then, in the "Print When" condidtion make is so that
the green one will print when the number in the box is greater than
zero and the red one when it is less than zero.