A few variations of Fall colors.
(https://cdnb.artstation.com/p/assets/images/images/068/672/333/large/fuzzytues-fall-is-here18-final01.jpg?1698366215)
(https://cdnb.artstation.com/p/assets/images/images/068/672/335/large/fuzzytues-fall-is-here24-final02.jpg?1698366219)
(https://cdna.artstation.com/p/assets/images/images/068/672/338/large/fuzzytues-fall-is-here23-final03.jpg?1698366223)
I guess you're a beginner (just 4 posts), so it's a start, but you can do better.
A good start to begin with such an autumn scene is presented here.
https://www.youtube.com/watch?v=3nQgPvacxno
I recommend getting realistic correct color values, just using photos with the desired scenery.
For your grasses, you can use for instance the RGB color tables, which you will find here.
https://planetside.co.uk/forums/index.php/topic,28215.msg280624.html#msg280624
And for autumn colors, you can create your own color chart.
So why not using some satellite images to get the right color values?
https://www.google.com/search?client=firefox-b-d&sca_esv=577057467&q=satellite+images+autumn+colors&tbm=isch&source=lnms&sa=X&ved=2ahUKEwiZk474qpWCAxU-_rsIHcWnDhMQ0pQJegQIChAB&biw=1904&bih=1055&dpr=1.76
What can help you tremendously is to watch the Terratuts Tutorials on YouTube.
https://www.youtube.com/@TerraTuts
Hope that helps you a little bit :-)
STORMLORD
A fine start indeed!
Based on the colors, I'd guess you're already following that autumn tutorial. I'd suggest checking your leaf image for dark patches or shadows, and editing those out in Photoshop or similar. That will help with those really dark trees. The green of the grass is a little bright for a fall scene. Putting a slope constraint on the trees will help the forest look more natural as well.
Thanks for the critique!