Forest Color - variation help

[TL1895]

Well, I've watched videos and still am stuck.

For example the dog tail meadow preset.
Is there an easy way to just have the overall colors darker without going through the enormous material?!
It takes quite a while to just find the forest color map in the multisub material created by FPP.
The Material rollout in the Forest object appears to have zero affect, even after running the itoo Material Optimize tool.
The preset is decent, but I want to be able to easily (in just a minute or 2 ideally) add color or variation and or overall color and tint changes.
Under a deadline now, so please understand I know there is more learning for me, but now it's just about getting finished, lol.

Using Max2019 and Vray Next.
Thanks

[Dragan]

Hi
Under deadline pressure and for Vray Engine some times I use a trick to reduce/increase value for Receive GI.
- Select FP object >> click the right mouse button >> Select `V-ray properties`>> Receive GI
- try to decrease the value to make overall colors darker
 

[TL1895]

Thanks for the tip, it is a good trick 

[TL1895]

Thanks for the tip, it is a good trick 

This was helpful in a rush, but my original question still stands.  Any help is still greatly appreciated.

[Rokas]

Solution for this is being developed.

Here is Sneak Peak:

[TL1895]

Looks promising, and simple....now the waiting 
Thanks