After some more research, I don’t think I can properly create something like this. Materials do not support looping structures, which is essentially what I need to continuously add new dots.
The closest I got to my goal, is by copy pasting the logic, and adding them up. In the blueprint I adjust a single dot each second. It works, but it makes the material fairly performance heavy, which is what I was trying to avoid.
The colour mixing was extremely easy, in case someone wants to know. Just put the blend mode of the material to “additive”.
I might attempt to deform the dots into more random blob shapes at a later date.