Stop cell size expanding when adding colours on a pivot report

I'm creating a roadmap using a Pivot report of Features per Release. Without any colouring the cells in the table have sensible spacing and they all fit on one page. Adding colouring of the cells makes the cells double in height and now the report won't fit on one (PDF) page, see the screenshot with and without colouring. I was told this is not a defect, but expected behavior... :-(