Ray,
Do you know if the other components in an oil paint could affect the pigments? I first thought not, but then each cie probably have their little secret mixes.
M.Graham uses walnut oil, while I think W&N uses lindseed oil.
In the mean time, I will just grab a tube of French Ultamarine from W&N or Atelier (if easily available) and solve my problem. I trust that various bran of oil paints can be mixed together, and that I can still any oil medium or kind of oil. Is this correct?
Thanks