I found that because the images were acquired at different date, and probably because of different atmospheric effects of the images, the color will not be balanced automatically.
I decided to divide the area into three section trying to keep images from the same date in in the mosaic data set.
Color balance did a better job but still did not produce a seamless image.
Jie,
I do not know why you think seamlines could cause color balance problem. I regenerated them to be sure and did not get different result. here is the seasmlines for the three mosaics.
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,Regards
Mohammad Dashti