as I mentionned in my answer above in this post: "For white gold, I prefer when possible the Pd 210 instead of standard Pd180 as the higher concentration of Palladium looks more white as Pt".
Palladium is in the same family as Platinum.
usual WG case are a combination of 750% gold, 180% Palladium and other metals for the remaining 70% to reach 100%.
Pt WG case are a combination of 750% gold, 210% Palladium and other metals for the remaining 40% to reach 100%. Then the final color is whiter, closer to Pt color than usual WG.
For instance, Laurent FERRIER has chosen Pt WG combination for his collection.
Hope it helps,
Cheers,
Patrickh