We have a light brown latex paint that we use on the Modules.
Edit 3/21/2013 Add paint mix. I took a small part of one of the modules to the local hardware store and had them match the paint color. This IMO is a pretty good base under most any scenery detail.
Benjamin Moore & Co.
Interior/Latex/Flat N215 Regal Premium Flat.
Base N215-3B Quart
BK 6 1/2 shots
BR 2 3/4 shots
OY 13 shots
We had done a thread a while back on basic Rock Color. I pulled some information from a Kalmbach how to book. There are several earth match colors listed in this thread.
Copy my post of this thread link . February 24, 2013 Help with painting plaster rock molds. Several base paint colors listed.
It is usually a diluted wash of latex paints. Carefully looking for the high-lighted detail you want. I would practice on some of the scrap generated for the very nice wall that you built. Lighter is usually better, you can always darken it down with an india ink wash.
Rocks Click on the underlined phrase to view a slideshow.
Noted on a previous thread was a How to: book Realistic Model Railroad Scenery By Dave Frary. Kalmbach. Great reference source.
Here are somes choices from the 2nd edition of the How to listed above.
Copied from page 24.
Latex Mud and earth colors.
Earth:
(1.) Tru Value Hardware Tru-Test No. C220 Dusty Sage or No. C216 Antelope.
(2.) Pittsburgh Paints: No. 3491 Franciscan Gold, No. 3610 Poplar, or No. 4489 Tulip Wood
(3.) Sears Easy Living No. 600 Autum Wheat Dark, No. 589 Sage, No 574 Parisiene Beige, (satin finsh only- this is OK because after thinning the paint loses its shine), or No. 068 Sand (a good light earth color).
(4.) California Paints: No. 35C-3D Boca Raton or No. 35B-3D Cameron, (a little on the red side but good for rich farmland).
(5.) (Sherwin Williams Fringed Jacket is an earth color that I haven't tried.) Noted penciled in add in my book was SW1118.
Mud:
(6.) Tru Value Hardware: Tru-Test No. C214 Sugarloaf.
(7.) Pittsburgh Paints: No 4491 Leather Vest, No. 7483 Earthenware, or No. 4606 Yorktown Brown (reddish).
(8.) Sears: Easy Living No. 585 Guernsey Beige
(9.) California Paints: No 35C-4A Oakheart or No. 36C-3D Cassel Brown.
Color names and numbers change with home decoratiing styles. Most stores have a cross-reference book to match old names and numbers to their replacements. Ask the store clerk. If you still cannot fine the exact colors mentioned above, use your color chip to select something else.
These colors are only starting points. Your own taste or the prototype you're modeling may differ, so feel free to substitute colors you like!
Also buy a quart of flat white for lightening and use with tinting colors. If the earth or mud seems too dark, add flat white before diluting the paint.
Best wishes on your project.
Mike CT