Beni,
While there is not an automatic way to color match across an image mosaic in Global Mapper, if you open the Control Center, select a layer, press Options, then go to the Color/Contrast Adjustment tab you can manage the relative strength of each color channel and manually get a better match. The v10.01 release also adds a Color Grade tab for further color management.
There is not any way to export a single layered file from Global Mapper.
Let me know if I can be of further assistance.
Thanks,
Mike
Global Mapper Support
support@globalmapper.com