calculate plastic per layer

I was wondering. I see online that you can cut different colors of plastic and then put them together to make multi color printers.
I have a good printer but its not amazing as a high end or business class one.
My question is there anyway to calculate how much plastic is used per layer? because I would like to offer a service on 3dhubs to do multi color prints. But I don't want it to be just generic meaning I cut some colors splice them together and thats how it turns out. I want them to be able to specify I want color (X) on 25% then color (Y) from 26 to 42% then color (z) from 43 to 100%. I know there are extra things I can purchase which auto splices it and calculates it but those are like 800$ which I might as well buy a whole new printer with that.
Is there a program that can easily calculate it based on layers or what would you guys suggest??

If you're using relative extrusion coordinates it's a pretty trivial programming exercise in the language of your preference to extract all the E dimensions from the G1 moves and sum them. Then you'd just need to programmatically recognize layer changes. If you're using Z hop you'd need to disregard any Z moves that are immediately followed by a move in X and Y and then a negative Z move.

If you're using absolute extrusion coordinates, the programming is only a little trickier.

Or you can use the filament change Gcode (I've used it before, it seems to work)

M600

You need to enable it in firmware though.