Thanks for the files. I see you are not using correctly Forest Color:
- It must be aplied to the texture you want to tint. I.e. to the diffuse slot of the grass. In this case there are multiple plants, so to each one of them. You can use "Material->Optimize Materials" to apply FC to all materials with a single click.
- The tinting map (where you want to get the color), is assigned to "Forest->Material->Get Color from Map" (globally), or to the "Override" section of Forest Color (if you want to redefine it locally). This map must be a simple bitmap texture, without Forest Color.
The Autumn Park tutorial
may help you to learn the Forest Color concepts. And here
you can find more information about tinting map, together a sample scene.