+1 on the Conti Retro Rides! And I'd go with the darkest brown you can find. Think it will really complement your color scheme on the bike.
I had those Conti's on my Desert Rat-ified Columbia. They rode great, and are being appreciated now by another g-Rat-ified customer in Phoenix, AZ.
Also, I didn't like the reflective stripe or graphics either. Used some 'Plaid' (grey / brown) acrylic lightly applied with a cloth to age the sidewalls a bit.
Before the aging:
View attachment 95742
And after:
View attachment 95743
The brown tones (mine were the 'clay' color) take on a look of crispy - glazed tires that are really old. You could get an acrylic that would be close to whichever tire color you end up with.