Please allow me to give my 50cents to add some tips and hints here...
In a former thread I had made some true life colour charts for greens and grasses
This could help you tremendeously to find your perfect colours for your scenery which looks very natural.
https://planetside.co.uk/forums/index.php/topic,28215.msg280624.html#msg280624Thread True Life Grass Colours
If you like to create fake grass as well, then maybe you would like to use this screenshot as a good starter.
Screenshot Shader
Fake Grass by dhavalmistry
If you use many colour variations in grass, greens, earth and clouds, then you will receive a more lively result.
Here is one example of an older creation. Take notice of the colour variations in the greens here. -> it looks appealing and liveley!
The plants here are from XFrog but I retouched their original leafs and trunk textures. As originals they look often very dark and sometimes poor in color.
A little bit Photoshop here will give often a much better effect in your image. Forget their originals... retouche them and end up with amazing differences!
(Execute auto contrast, do some brightening corrections and improving the color dynamics here is mostly the key.)
Lake Tahoe
Pay attention to the colour variations in greens and bushes, the different water colours including the small wet sand stripe and the different clouds
Another point to pay attention is lightning. Often others display pictures here which are very dark. It is important to find out a good lightning to brighten the picture.
If you don't pay attention here, the result is often poor and looks somehow dark. A good lightning is truly essential !
I guess, its better to place the sun position slightly behind of your camera position. This causes the sun to brighten up the scene in front of you.
A good sun position for my Lake Tahoe scene
Please notice the bright trees because they're lit from the front (as seen in the picture Lake Tahoe above)
If you place the sun ahead of you then the shadow of trees, bushes, obstacles ect. darkens the scenery which lies ahead the camera. It darkens the scene, you look at shadows ahead of you.
Just do it in the other way round. Place the sun behind you (to illuminate the scene ahead of you) and set it in a way, that it will cast a slight shadow left or right of your greens/landscape.
Try different sun positions and altitudes and maybe setting a secound light or just increasing your Environment lightning in the scene can be very helpful.
Just try out what's best. I often do first some small renders with very low settings, just to find the correct lightning. Followed by a bigger and better rendering to crasp more details.
I did a little bit poposhop retouche to show up the difference in your scene.
Lightning up dark shadows and brighten the colours
By changing the sun position and lightning you can also give a try increasing the contrast setting in the tonemap tab.
Rendering ocean scenes where you see much water and sky, the difference is very dramatic and much better than rendering the picture with it's original 0.2 contrast setting.
I earned great results in poor skies by only changing the value from original 0.2 up to 0.5-0.6. It's sometimes really worth to try it but it depends on the scene and view.
Often overlooked / contrast settings in the render tab
Editing contrast can give you a much more natural or lively result in a sky or water rendering
STORMLORD
