Here is a quick tutorial on how to paint green and beige marble.
1)Start off painting the tiles your base color I have used Dheneb Stone for my tiles
2)Using Thinned Devlin brown wash apply little pools or puddles of brown on the tiles themselves and let dry
3)Do this a couple more times leave some spots with just one coat of wash and go over a few a couple of times to get darker patches
4)Using Green (Dark Angels green) thinned down I painted the alternating tiles green like a checkerboard,leave the paint thin enough so you can see the marbling underneath but it should not be too watery either.
Add a layer or two just like you did the brown to make the green darker in spots
5)Using white(VMC foundation white) very carefully paint veins on some of the green tiles and you are done.