I have heard about it before but never applied to gained knowledge until recently, when painting gold instead of using black try brown it gives you a better gold color, here I have two of my old Space Marines with gold
Compare them to my new Space Marine with brown under the 2 techniques I used to paint gold.
the first is plain Shining Gold over Scorched Brown on the shoulder pad rims, it still lacks the Burnished Gold and Mithril Silver highlights.
The second is Mithril Silver over Scorched Brown followed by the first Grypone Sepia wash.
For me the gold parts are better defined and richer when I use brown. what you think about it.
Minor update: I corrected some cases and words, added the word wash after the second technique and added the word Gold after Burnished in the second paragraph.