Gerber Composer 6.5 to ONYX color issues

Composer is a terrible program to use for digital printing. It uses vinyls and fill colors, which can royally screw up your color. Since you have illustrator, I would recommend learning it to do your designing

 

Composer is only terrible if you don't know how to use it - just like Illustrator. It's a great program for designing signs in - even if you're going to be digitally printing (including other than Edge prints) I'm sure there are just some settings that are not tweaked the way they were before. I would be looking first at your export settings. Also, as a general rule, outside of a properly color managed workflow, you'll get better results using RGB colors. Which pallets are you using? That can make a difference as well.