When I made my buff Silkies 35 years ago, it took me 3 generations to remove the blue underfluff from the initial White x Buff cross.The hardest part in breeding good Buffs, in any breed, is to keep a good depth of buff under color, and lack of light shafting in the feathers, while retaining a pleasing buff top color.There are those working on them. When you hear about European or Dutch red silkies, they are close to RIR colouring. Or at least they were before importation.
http://www.aviculture-europe.nl/nummers/10E03A15.pdf second page
And this is a pair (closer to New Hampshire colouring than RIR, though) that were auctioned on BYC about a year ago:
As for buffs carrying blue, I would not say it is either common or not. There are many factors pther than blue that can make a buff lighter in tint. My point was that blue dilutes red pigment SLIGHTLY, not a lot. Lavender, on the other hand dlutes red A LOT.