More often than not, they seem to appear as black on top, red below the waterline and with a thin white "boot top" stripe separating the two main colors.
I've seen photos which seem to show overall black with just the white stripe at the waterline or just overall black with no stripe. But there aren't a lot of really good photos. The best ones that I've seen show the black/white stripe/red scheme. Here's a photo of the general arrangement but the color isn't that good:
This website has a few decent photos showing Russian subs in drydock, though a lot are black & white.
I'm building a few subs myself, including 1:350 Typhoon (have to modify the DML kit to get the correct stern), and the Zvezda 1:350 Kursk. The latter seems to have a black-red hull, as explained above, though I've seen no evidence of a white boot topping between the two colors. The Typhoon is an enigma to me, as there are few color photos of the boat in drydock. My best guess is that, from top to bottom, it is black, with a dark gray band, followed by a red under hull. There are also some white/light gray areas for the sonar window and such.
Actually, I would appreciate some help in this area myself, as I'm new to sub modeling.