I have a couple thermometers that Do-it sells. To me a thermometer is very important. Blue always bleeds no matter how careful I am. It's best to just make as much as your going to inject so you don't have to reheat much. With blue glitter I heat my plastic over 350 degrees to change it over then let it cool down to 330 to put the glitter in. Then shoot right away. I don't have a problem with Do-its red so I'm guessing your getting your plastic way hot. Too hot of plastic will ruin most any glitter.