I work as a consultant in fine art reproduction, they goal for my customers has always been to reproduce colours exactly as they appear in the original painting, I can offer the following advice:-
1. Forgot Passport it does not have enough colours to be useful for this application, I use a chart with a palette of over 1000 patches that are tuned to the gamut of art medium being photographed ie oil, water colour etc. If producing and measuring your own chart is out of the question use a colorchecker SG or Kodak IT8 not ideal by any means but a step up from Passport.
2. Shoot RAW but do not use ACR for RAW conversion it does not have a wide enough gamut to accommodate all the colours you may need to preserve, it is also built for speed not accuracy detail smoothing and demosaic errors will appear. I use a heavily modified version of Rawtherapee that includes slow but accurate demosaicing my own input and output spaces tuned to fine art and is floating point for greater accuracy and detail.
3. Use a high quality balanced light source around D50, and set white-balance in the camera, you should not have to play with the white balance after the image is taken.
4. A good LUT based input ICC profile is critical to reproduce colours such as Cobalt Blue accurately.
I hope this is of some help!