I found this perlino coat Andalusian at Bandywine drop in roanoke valey. You can get it as early as chapter 2. They have 2 extra health than the dark bay Andalusian . : r/reddeadredemption
This is Sleepy Eye, she's an Andalusian with the Perlino coat. She's a war horse sporting 10 health & 8 stamina @ max bonding. She doesn't scare easy & is hard to
Red Dead Redemption 2 Wild Horse Breeds Locations Guide - RDR2.org
Historical Accuracy - "Inaccurate Horse Breeds" | The Red Dead Redemption Amino