I have heard that when a salmon first enters a river from salt they are still attracted to the colors of the sea. Blue, white, black, silver, green and gold. As they are in fresh water a film forms over their eyes for protection from moving sand in the river. They have no eye lids. This gives a different available spectrum of color and changes to orange, red and purple as the season progresses.if you look at the tips of the natural butterfly (the ones that are fluttering along the river) there are 3 colors follow that from body towards the next color we are at blue next is orange, As I said not a person that ties though gonna give it a shot. My flies are based on the enviroment I say with the weather in another week we will be fishing an orange pattern.