Heres my small #6 deceiver fly complete with foul and weed guard. These bass in this creek love purple.

I think its a spring early summer thing. If you look at there forage under different lighting situations purple is the color that shimmers with indirect lighting. It will go to a blue color too. With direct lighting it will be the color that shimmers that are lighter.
Also small panfish that are green are the same color as purple under water. I think the scales and fish slime refract the color we dont expect.