I recently listened to an old podcast from Basic Brewing Radio and they did an experiment using water built from R.O. specifically for stouts (dark beers) and one specifically for pale ales (light colored beers). They also brewed the pale ale with the stout water and vice versa. The results were that these beers didn't taste nearly as good when they were brewed with the wrong water.
My question is, where can I go to find help building a water from R.O. for a particular type of beer?
Are there published standard formulas for water additions for each style of beer?
As far as I'm concerned trying to target water profiles is a waste of time. First you want to dial in your mash pH(Bru'n water, Bru'n water, did I mention this thing called Bru'n water), then use gypsum/calcium sulfate (CaSO4) for a hoppy beer, calcium chloride (CaCL) for a malty beer and half and half for a beer in the middle. That's all you need. The rest is a waste of time. And this is coming from one of the most analytic, detail oriented brewers you will ever meet.
For dark beers I do the Gordon thing, mash the lighter colored malts (base malts, crystal malts, victory, biscuit, etc.) and throw the dark/roasted malts into the sparge water (or steep them) so they don't screw with your mash pH.