I've always had a problem trying to find an analog to Citadel paints when I want to use Vallejo or Reaper. I found this handy app called Paint Converter for the iPhone. It gives comparisons as to what paint matches each brand.
The only brand of note for miniature painting would be P3. But they seem to do their own thing.
Apple/iTunes link: http://itunes.apple.com/si/app/paint-converter/id465643256?mt=8
Android link: https://market.android.com/details?id=com.hexxus.paintconverter