I'm the proud owner of two YG watches: an 1815 manual and a Patek 5107J. Much as I hate to say this in this forum, the YG alloy that Patek uses is significantly warmer, deeper, and just nicer than the YG alloy that Lange uses. Lange's YG is a simple, almost brash yellow; Patek's is more complex, and the hue is somewhere in between other brands' YG and RG. I have noticed this difference on other Patek and Lange YG models. I'm curious whether anyone here knows what might be causing the difference?