That is why I said the sheath should be pretty much translucent......may have said the opposite by mistake.......and sparse......with the body being a bright color to be seen through the sheath. But, I think a hint of Amber color in the sheath works well.
I think you will also find that the Antron sheath was selected by Lafontaine as it trapped air bubbles which mimicked the gas bubble caddis emergers are said to expel to help them reach the surface and break through the meniscus.