Well, we had the blue water type on the B747-200s we operated for Air Atlanta from Tunis Airport, doing regular flights to/from southern France, some years ago now!
I was operating the airplane on the initial flights, and when we returned to Tunis I was asked by the ground maintenance crewchief if there was any toilet servicing carts for this airplane type at the airport, since Tunis Air only had A320s and the like.
Why he asked me I don't know, but I didn't know about such things, and answered in the negative!
Minutes later, obviously pissed off, he had released both dump valves and unloaded both full holding tanks on to the tarmac, luckily in an area slightly away from the terminal building, though on brand new concrete tarmac!
I called 'Ground' for help with getting the fire appliances over to wash the stuff away, but they wouldn't help, not a fire! - so it soaked right in - and as you know, new concrete is like a sponge with stains!
As far as I know, there is still two rather large blue stains on their newish tarmac area!
