1. I dip the next color right away. Just give the disc a good rinse under water to remove any dye sitting on top of the plastic first.
2. Red put directly onto the blue woulda given it a purple color. You could have dyed the blue first...Remasked it...then dyed the red. When doing single color dyes there is no need to remask
Also make sure to put the disc into the freezer for 24hrs after dyeing to allow the dye to cure properly. Make sure to mix up you dye well. This will help prevent the splotchy color you got on the smokey dye. Give the dye a good shaking to dissolve all the dye particles.
I did a baseball dye a couple of months ago. Dyed the blue first..Remasked...Dyed Red.