How to make striking glaze drizzle? In this video the chefs drizzle two colours across their cakes:

https://youtu.be/EJsUDT9Z_Io?t=11m42s

In the comments the presenting chef explains that she doesn't know what that drizzle is but that it could be food colouring and condensed milk.

Having tried this and found it ineffective, I have to ask how else could this very striking colour be made without it fading or melting into the rest of the glaze?
It’s cocoa butter and colour. Probably powdered colour for best results.