Looks like something a Scott Sanchez double bunny would imitate nicely. Easy to "match the hatch" colors with that pattern.
Can't recall ever seeing any whitefish under about 5-6", and those were not nearly so brown on top. But coloration on whitefish seems to be highly "system dependent" with a great range of coloration in the adults. On the Big Lost tailwater at Mackay ID, the whitefish have a pinkish tone, which speaks to their isolation, and why they are protected on that piece of water.
John
P.S. Strikes me as curious that there are no salmonfly nymphs in a place where the golden stone nymphs are prolific.
The fish are always right.