US 10 for AE
UK 9 for carmina rain/forest
vass 42.5 for P2/F
I have both Vass oil green and G&G racing green and while both appeal to me, the difference between them is visibly stark.
To my eyes, oil green is a lot greener, a lighter shade and muted. Racing green is darker, richer and at night looks like anything but green, it only shows when you're out in sunlight.
The Vass oil green is box calf while the G&G is (I suspect) crust leather, since it takes burnishing rather well.
I am happy to be corrected on technicalities but that's how I see it.
38.5 way too big, I think you are better off with 38 or better, 37.5. If you have high instep, 38 might probably work. I am smallish UK6 and 38.5 on the F. IIRC, some one with UK5.5 and a high instep went 38.5 on the U.