Dutch,

Here’s a vid confirming the test. Though it adds water to fluid the chemistry is the same. But, you may see results more clearly.
https://www.youtube.com/watch?v=0aMf3I0ez5s&t=15s

At present it suspiciously looks like you may have Dot 5.

If any doubt and because of the seriousness of messing with brakes may I most respectfully suggest you take the test results to a brake shop for a second opinion.

Let us know how you get on.

Regards

Geof
70th Anniversary 4/4 (Duratec 1.8), model 1995