Unfortunately, as far as I know, camouflage schemes were not carried as
standard by any S-100 class boats - the only known use of camouflage on
S-100s was as an emergency measure when the boats were travelling
between bases in the daytime. They weren't camouflaged in operational
use, it was found that the overall pale grey/white scheme actually
provided better concealment at night.
It's the earlier S-38 class, with the unarmoured bridge, that had the
famous "splotch" and "tiger stripe" camouflage schemes. These look a
lot like the S-100 at a glance, which is probably the reason for the
misconception that S-100s were camouflaged.
(There's a long discussion on this subject on the Modelwarships.com forums, in the "Calling All Ship Fans" section)
Whilst this means you're rather limited in your choice of colour
schemes for the Revell kit, it does make it easier to choose the right
paints (even if colourblind), as it's basically painted in different
shades of grey, from very pale grey ("Schnellbootweiss") for the upper
hull (Revell advise using a 50/50 mixture of white and light grey for
this), to almost black for the lower hull below the waterline (I used
Tamiya "NATO Black") The deck is a slightly greenish-grey (Revell
suggest their "Dust Grey" colour for this, which is what I used, and
it looks OK), and the wooden parts of the deck would be in a bleached
wood colour (although I think the wood parts were painted the same
colour as the rest of the deck on some boats).
Hope this info helps! Sorry I can't give more advice on paint mix
ratios - the only paints I have recent experience with are Tamiya and
Revell acrylics.
This page may also be of use:
http://www.prinzeugen.com/colors.htm