Black and White Photo Reference for a Color Portrait

I teach a week long oil painting class at Common Ground every summer.  This year is ancestor portraits.  I am anticipating several students wanting to use black and white photo references of parents, grandparents, and even great-grandparents.   I used this photo from 1902 as a reference for a painting:

and this was the oil portratit, Senex, that I did from it:

Senex by Jaime Cooper

Adding color in your head when using a black and white reference really isn't difficult if you have enough experience working from live models.  I can kind of see what color it should already be.  It shows you that value is much more important than color, I will do a post on that later.  I would have a much harder time not having a reference for the values that should be there.

If I get stuck on the color I will use a live model that I imagine to be a close match for the skin colors or another work of art as a reference.  Rembrandt's portraits are a favorite for me, including this one (I feel incredibly deficient using a Rembrandt painting in the same post as one of my own paintings, but there you go):

 Rembrandt Harmensz. van Rijn, An Old Man in Military Costume, The Getty Center Los Angeles