No matter what, one thing is guaranteed. The cement under your foundation will eventually discolor. This is just what cement does over time. How soon this happens depends on a lot of different things, including weather conditions, proximity to trees, etc. One way to eliminate this, and a way that a lot of people are choosing to do it, is to install a granite slab under your monument. We actually install this slab over the wet concrete so that it's stabilized and is guaranteed to never move or lean. This is a very cost friendly way to ensure that your monument will always look beautiful.
The advantages of this include:
1. It will never crack or discolor
2. It will not chip or break when hit with mowers
3. You will never have to worry about replacing your foundation. It will look as beautiful in 20 years as it does the day that it's installed.