I’m doing a series of animations illustrating probability data, represented by a field of red and blue spheres. I want to show how the mix of red and blue can change and I want to be able to change the amount of red vs blue balls throughout the animations (for example, go from 10% of the balls being red to 80% of them being red)

an example of what I’m working on

In an ideal world I would animate the red/blue gradient on the colour property. I can achieve exactly what I want by moving the position of the red and blue along the gradient, but since this is not possible, what I am doing is animating a layer of all red and then a duplicate in all blue. Then I use a layer mask to ‘switch’ certain amount of it from red to blue by cutting more or less holes in the mask.
Before I continued with that method, since there are so many creative ways to accomplish anything in Stardust, I thought that I I’d ask here if anyone has a better idea for animating a change from all blue to all red particles over time?
I’ve played around with all kinds of things like a duplocate with a different seed, offsetting time, duplicating and changing birth chance, etc
My masking method will probably work just fine,  but since its only my second day in Stardust who knows what creative solutions I might be missing out on!
Loving Stardust!