“For highlights use flake white added to lemon or orange chrome, lemon chrome straight, or orange chrome with lemon chrome and dutch pink.”
From Frank Atkinson’s “Scene Painting and Bulletin Art” (1916, page 165)
Here is an example from Fargo Scottish Rite Treasure Chamber (15th degree) that has coin highlights illustrating the addition of white flake to lemon chrome.
This example from the Winona Scottish Rite Treasure scene shows the use of lemon chrome straight as the final highlight.
The third example depicts the use of orange chrome with the addition of both Dutch Pink and Lemon as a highlight.
To jog your memory, here are the colors that we are talking about:
1.) Lemon Chrome (my dry pigment, ca. 1980s and paste from Cobalt Studio):
2.) Orange Chrome (my dry pigment, ca. 1980s)
3.) Dutch Pink (dry, ca. 1980s)
The one color that is not mentioned is what I have come to know as Chrome Yellow and is frequently utilized in treasure scenes post-1920s. Prior to this time, the mid tone and highlights mainly derive from a lemon yellow that is warmed with an orange or dutch pink. Chrome yellow was available in light, medium, or dark. It is very different from the lemon chrome version, which is similar to a primrose yellow (where there is a lighter value and cool hue)
This is from my stock (medium chrome yellow, ca. 1980s)