The colors of my terrain details are different than they were before adding Nature Renderer.
Since version 1.2.0 and later, Nature Renderer uses the same coloring method as Unity. So the color of your grass should be the same before and after adding Nature Renderer.
Read more about colors in this article: Change the colors of detail objects.
For previous versions
Nature Renderer uses a different coloring technique than Unity's terrain details, so you have to tweak your color settings. Nature Renderer color corrects your detail objects to match exactly with the colors set in the Healthy and Dry settings. So, if you want your grass to be green then you have to set the Healthy/Dry colors to green.
You can set both the Healthy and Dry colors to white to disable coloring and use the original color of the detail object.