If you look at the comparison between the Real Life photos versus the Flight Pro Sim screen shots, note the difference.....
I had the same problem with the California/Nevada/Arizona, etc, scenery in my FS 2004, (where I spend most of my flight time).
In real live the ground textures are brighter (and dustier), as can be seen from real photographs, NOT the lush green textures of the default scenery.
I cured this to some extent by "brightening" the overall textures with the aid of Ground Environment Pro's RGB "colour" modifications, (and slightly reducing the Autogen complexity).
It works fine for areas of the World which can be dry and dusty at times.
I generally find that the default ground scenery is far too "dark", and does not represent a bright sunshine day...

...!
Brightening up the overall scenery areas gives a more realistic representation of real life Summer textures!
Paul....G-BPLF...FS 2004... 8-)...!
http://www.flight1.com/products.asp?product=gepro