Since your painted background hills are further away than your hills that you will be using the ground foam on, don't know if you need or want exact matches. When doing trees folks often seem to mix the colors to simulate shaded and brightly lit areas. If you really need to match the color, take some of the material you want to match to the store and have them mix some for you.
Good luck,
I have been thinking about my backdrop colors. I am modeling Eastern views and will probably paint (or try) some hills on my backdrop. (I have seen the posts here on how to go about it and have saved them as a reference for when I get ready to actually start painting.) I am using WS ground foam in the three basic greens they come in. Since I am a big fan of using water base paints and scenery methods, I will be using acrylic paints. Probably those that come in the plastic craft bottles that Wal-Mart and Michaels carry.
Can anyone provide me with brands and names of colors that they have found to work right, straight out of the bottle without mixing colors? I know that I will have to lighten them up for distances, but I am looking for a close match to the WS ground foam colors first. I am primarily looking for the greens, but the other colors will be welcome too.
Thanks.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.