I did maths

I found some truly horrific.

Base off of my maths the rainbow factory at a flow rate of only 0.1 meter per second (0.22 mph) for only 4 feet wide would require 29 fillies to die in on second if the guy had one gallon of colour. Which is about 100000 per hour. you see where this is going, the amount they would have to kill is not even realistic amount to actually achieve. So forget about all other questions, the true question how could they even sustain such a thing. Plus that was only one rainbow. Even if they had other ways to make rainbows base off of my maths why would they even bother with the fillies? What I know, I'm no sciencetist.