Male Ephemerella excrucians (Pale Morning Dun) Mayfly Dun Pictures

I wonder if this is the invaria rotunda variant or not even in the invaria complex.
I am not a entomologist but it is a odd one.

Would some of the entomologists on the site comment on the color of this sulphur dun? I was scanning through the images, planning on doing some dyeing, and this one caught my attention as it is so much darker than others.