It pays 6 coins in the Green worker phase.
I suspect the main reason is because it's easier to count your coins and multiply by three.
Thanks for the first pat of your answer and I confess to being too thick to understand the second part of your answer.
Different cards have singled coins of value 1-6, but there are a few with 2 3 coins side-by-side.
How should I understand your second answer in terms of a single "2" or "4" coin? YOu could represent "4" by a single "4" or by 2 "2"s.
I really don't understand the multipy by three part. Sorry.