You can use the dye as a tracer, but it's not necessarily easy. Let's start with a few basic questions:
Does a single sample contain all three sizes of particles (a mixture), or are samples containing only a single particle size?
What is the polydispersity index of the particles? I.e., if they are "5 micron particles", that's an average value. You will need to know what the variability of the particle diameter is. Also, you should measure it yourself if you can.
When you want to "quantify the PS-MS of each size in the sample", do you want a mass-based or number based concentration?
Is the dye in each size particle the same, is the concentration of dye in each size particle the same, and have you ascertained that the dye does not leach out of the particles over time?
What is the concentration of dye in the particles and the approximate size of the particles? As a starting point, you should try to determine how many dye molecules are in each particle?