Not to take it off topic, but if you use Prestone Any Color, you can relax a little bit with having to get every last spec of dex out of your system. Some of that stuff can continue coming out for days worth of fill up > run > drain.
Just makes things a little easier.
I flushed and flushed until the water was coming out absolutely clear, but then I filled it up with any color, drove it for a week and peeked inside the filler neck, was a green and red mess.
Drained it all out till it came out clear again, refilled it, looked inside just a few days ago and it was all green and red mixed again. Gunk just keeps dissolving out into it I guess.