The thing that ticks me about Pantone, Behr, Sherman Williams or
whatever is that they're proprietary systems and RGB is the "Open
Source" solution, going back to basic principles and should be
communicable to the proprietary mixer systems, but not the reverse.
BTW I have a 2nd hand Pantone guide right here, it reads out to "three
parts pantone light red and 1/8 part ..." yadda.
John A.