Thanks for the answers re Matmatic and Parmatic, bb.
And for the detailed explanation about the HSV correction - it begins to make a bit of sense.

But I still don't get the bit about multiplying an RGB tuple ( c ) by an HSV tuple ( HSV(c,...) ). Presumably, Poser Python knows that one of these is an 'apple' fruit and the other one is an 'orange' fruit, and it converts one of them before multiplying them together to determine how much fruitiness we have in total.
Hope you see what I mean...

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)