For colors, I used Lure Craft and MF exclusively, so I can't speak for Do It.
I'm assuming you mix the fluorescent colors before heating the plastic? I always made sure the color was mixed really well and added to cold plastic before heating and never had any problems.
LC and MF are very different, but both serve their purpose. Couple of examples.......I preferred MF motor oil to LC (LC seemed to change their mixture a few times over the years,) and MF's pumpkin was very light no matter how many drops I added, but LC's pumpkin is dead on. Just something you have to play around with.