Why two-tone de-icing fluid?

Factual Questions
1

I took a flight back in November and they had to de-ice the plane before we took off. What surprised me was that they used two different types of de-icing fluid, with different colours and viscosity. (Is that the right word?)

The first spray was the bright putrid pink that I’m used to seeing. Sprayed it all the wings, it ran off the wing onto the tarmac. Plane started moving again. "“Off we go!” I thought to myself, which was good, since I didn’t want to miss my connexion.

Well, no. The plane taxied forward a bit to a second de-icing station. But this station, they sprayed neon green stuff onto the wings, and it didn’t flow off. Instead, it looked like lime-green sludge. Stayed stuck on the wings. As the plane taxied to the runway, it looked like it had bright green wings.

Plane taxied to the runway and this time we were off. The green stuff stayed on the wings through the take-off, then gradually started oozing off as we gained altitude. After about 10-15 minutes in the air, it had all blown off.

So why the two different types of de-icing fluid? What was the difference and purpose ?

2

The pink stuff is to melt the ice. The neon green stuff is to keep more moisture from sticking on the wings and freezing.

3

Why have I never seen it before? Is it new?

4

There are 4 different types of de-icing fluid. The main difference is the duration of their effectiveness. The longer-lasting stuff is also going to be more viscous so it doesn’t run off as fast.

Here’s a video about de-icing procedures from Mentour Pilot that explains the different types of de-icing fluids and their purpose: The secrets behind De-Icing! - YouTube

But, kunilou is right, the first treatment was likely just to remove existing ice buildup. The second treatment is designed to stick to the skin of the aircraft until they reach a certain speed (the one they need for takeoff, I think). It can’t stick to ice very well, and when the ice melts it dilutes the fluid reducing it’s effectiveness. This means you have no idea how long the treatment is good for and airline pilots won’t fly in a plane unless they KNOW it’s safe.