I have a rounded box on my report that my boss wants to change color based on a field.  I found conditional formatting on a field, but I don't know if I can apply it to the box. 

This might be crazy, but what about creating multiple sections with a different box in each. Then conditionally disable the section that you don't want to use? If you have a lot of fields this would be a pain. Another idea (which I've never tried before but it just came to me) is to only put the box in its own section. Then turn on Underlay Following Section for the main group. This would effectively make the correct box appear with the rest of fields and you wouldn't have to repeat the entire section each time.

Thanks to all for answering.... I talked him into allowing a colored bar instead of the dang circle.  I used highlight for the different values (only 3 at this time).