Thanks for the file and for using Dropbox.
I’m not sure if I follow with the “external effector” comment. Inside the Cloner, there is no option. (If that was the question)
Here are two examples:
In the first one , I use the gray values of the Step Effector to drive a MoGraph Color Shader, while the Colors are applied then via Colorizer.
The second file  uses a Plain Effector to enable color, but the clone color itself comes from the Falloff> Fields> Formula. Here the F parameter is used to animated the colors. The formula is id<f, then this means, while the app is processing through the clones, it checks if an id is smaller than the f value. If that is true (=1), then the color is used. If it is false (=0), then the Field will not influence anything.
(I exclude the two-child (white/red) sort/modify-clones setup, as it will create a more extensive setup.)
All the best