Nice report JC.
I (As yet) do not fish the fly. However, I do like to read a good flyfishing report and I do admire the artistry in both the casting techniques and the tying or a good fly.
My thought was the same as Frank. ie: Do some colours appear the same to a fish.
I know they can be fooled by artificial lures (Not bought for the purpose but..) such as:
1. A 2mm piece of rubber (My 3 braincells cannot think of the word I need right now so bear with me) outer covering - Black with white inner - to an electrical wire (old type) can be used and mistaken for hempseed.
2. A tiny slither of orange peel maybe mistaken for a maggot? or liked for the flavour it leaves in the water.
(My old joke was of a roach I caught when he took the pith!
I suppose the above answers the 'are they fooled' bit.
anyway, I waffle too much as you can plainly see.
All I wanted to say was: well done my friend.
As I read that report I was at your side! Good stuff!