Power BI's visualizations have colors assigned automatically. It should be possible to set a color when a value is reached (e.g. always show negative bars in red) or for a particular color in a legen...
Along these same lines, a more fine-grain control of formatting in general should be at the top of the list. Many clients won't even consider a reporting solution that doesn't match certain color patters exactly. I think this is the main thing preventing most people that I've talked to from adopting this tool. This forces me back to excel where I can control details.
