Ken:
Actually, when it comes down to it, Rio Grande changed the color scheme on their 'covered wagon' diesels at almost any kind of whim. When both the F-3 and PA units were delivered to the railroad, they were painted in black and yellow.
Then came the Grande and Silver 4-stripe and the Grande and Silver single stripe. Roofs and trucks were painted either black or silver depending on what the Burnham shops were thinking at the time. I don't think Rio Grande ever had a 'standard' paint scheme from year to year (or even month to month).
So I'd say that you're safe with your black, Grande Gold and Silver F-9's. Stewart has never been known for 'fanciful' paint schemes. In fact, Stewart was the first to produce the Rio Grande F-3's in the original black and yellow early passenger scheme.
Frankly, that's the color scheme I was looking for but couldn't find, and settled on the later Grande Gold and Silver 4-stripe scheme.
My F's are Genesis/Athearn. Strictly DC, but they're smooth, powerful and very quiet. And very nicely detailed. I only run them on my "Prospector" streamliner, because Rio Grande originally bought them as passenger units.
Never run them heading a freight, that's what my steamers are for, LOL! 
But I think you're prototypically safe leaving your F-9's the way they are. As I said, I don't think Rio Grande EVER made up their minds on a 'real' F-unit paint scheme.
Tom