Nice red soil on those bases - what's the colours used, please?
I standardised my basing color a while back (*.
It's Warpaints Brown. I got it from Mantic but think it's actually made by the Army Painter people.
Plus a drybrush with whatever lighter brown happens to be handy. It takes a sepia wash well too, but these aren't washed.
*) It's actually a slightly funny story. I ordered something from Mantic a couple of years back and needed to add a couple of euros to make the "free postage" limit, so I stuck in a pot of brown paint -- I have absolutely nothing else from the Warpaints range.
I used to use whatever was handy for basing using my regular colors, but the problem is that a big part of my paint collection is 20 years old Miniature paints which are no longer sold locally -- if I run out of a particular shade, I basically can't get it anymore. All of which led to a whole lot of disjoint basing.
So faced with this single bottle of paint that didn't fit with anything else, I decided to make it my standard basing paint used for nothing else.
Now I just have to order something from Mantic once a year or so to restock the basing color... usually it's the Xmas crazy box.