Need some artistic help: I've been using gray and black auto primers to paint Scenic Express foam block walls, which can be seen in upper wall of attached photo. Spray cans are easy to use and I paint them outside after cutting and pre-fitting. The lower wall viaduct sections are also foam and are shown in the photo - I purchased these at train show many years ago (I think they're HO scale but I like them and they look good), and they came with the color shown ~ a tan, golden, or brownish/rust color.
My question: for another project I am planning in another area of the layout, I will combining the grayish Scenic Express foam block walls with the remaining brown wall HO viaduct sections such that they join together (no separation like in prior project). I am not concerned with different scale of stone blocks. However, I am not sure what to do - paint the Scenic Express walls to blend with the brownish/rust walls, or vice-versa. I don't own a spray gun so am limited to hardware store spray paints. I've seen some nice retaining walls painted brownish with some black crevices in train magazines over the years - has anyone done this and if so, what color and brand have you used? I don't want to get into a lot of experimenting because I just don't have the time, and am hoping to get some good advice - pictures of your retaining walls would be appreciated. I'd rather not go the all-gray route because too much gray is depressing IMO - like my hair 
but if you have all gray walls I'd still like to see pictures...any pictures of walls of any color might be helpful.
