The Renegade Fly Pattern is a great classic fly and then just add purple make a great combo.
One possible reason why the color Purple (violet) may work on trout is the range of visibility under the water. As you go deep, colors vanish, starting with the brightest like red, white, yellow, orange, brown, blue and finally violet giving us a wider spectrum of purple options; maybe the trout when looking up and feeding they can see it better or maybe trout just like purple.
Subtle color shades, such as maroon, indigo, and purple can be effective when fly-fishing in clear water. Fluorescent orange, yellow, and chartreuse flies can be effective when fished in muddy water or other conditions when fish having a harder time seeing the fly, as can black and red.