Paint color referenced on a computer monitor, taken with a digital camera, probably an uncalibrated monitor, even more difficult on a LCD screen is dangerous if you want a match. The PPG or Imron colors are not that hard to reference, an auto color house (sell paint to bodyshops) should have one or the other or both in a book of samples.

All that said, "Merckx" bikes were made by Kessels, Colnago and DeRosa, and replicated by Eddy Merckx Bikes later, lots of variations are "correct", choose your builder first.