Google Sketch Up? I use Sweet Home 3D but it is mainly for floorplans. There may be landscape symbols and even surfaces to download for exteriors. Both are free.
Here are some other programs for drafting and so forth that have been recommended on this site:
Zbrush20/20
DraftSite
Chief Architect Premium
For color simulation? I use the virtual painting program from Benjamin Moore all the time. It is free. You have to download Adobe Air if you want the machine resident version. It is also free. You upload your photo, spend a little time masking off areas to paint, and then pick any colors from the Ben Moore collection. You can even adjust opacity. If you don't want to mess with masking off your own photos, you can pick one of their pre-masked examples that is close.
I use the DRAW program in Libre Office all the time and it would be adequate for adding simulated siding or something for exploratation purposes. Libre Office is free open source software.
Other than that, there are many landscape and exterior programs out there in the $40ish range that could suit your needs. There may be freeware versions that will show up in a Google search? I suspect most have free trial periods. As mentioned one drawback I found to the landscape programs is that many only allowed fairly small lot sizes. With any drawing programs, you may find it difficult to draw with a mouse. Drawing pads that would work for these things are under $100 now though.
Let us know what you end up working with please?