OK, thanks Bill and Eric. I'm happy to see that you both think it is important to compensate for the different colours - as that too was my thinking but I suspected I was wrong because I can find absolutely NO, NADA, ZIP reference to taking this into account on any forum posts or in any decent Zone System books ?? OK, it might be in one in an obscure place, but surely this should be first principles stuff that is commonly taught. (Assuming one is using a spot meter for metering and not an incident meter as per BTZS)

Why isn't this concept mentioned anywhere?