I've read them, along with Furrtek's and ChibiAkuma's documents but I'm still a little confused about where this palette data is held in ROM. (I do read that they are accessed from Palette RAM but don't they have to originate from the 68k program space first?)
I was expecting the colours of each palette to be in some form of a table. Looking at the above palette, I searched for the blue colours, "009E 51BE 04DF" (and other likely permutations) in the P1, P2, S1 ROMs but can't find anything close.
Are they stored differently and converted when sent to the Palette RAM?
They are stored at $90000 onwards in the P1 ROM.