I am doing a data synchronization and just before I performed a structure synch so that they would be the same. Then I get the error below 5 times in a row, it rolls back, and continues with the next table. I've checked this table on both servers for any NULL values and the query can't find any on either table.

[Err] [Dsy] [FTargetSrvX] mysql_real_query error: Column 'custom_color_fee' cannot be null

If you're sure there are no null values anywhere there, check to make sure that it is including that column in the synchronization. Omitting the value might assume NULL and cause that error.