I'll actually revisit this immediately.
A cute finnish couple did a youtube video about bicycle disc brake vs lathe. The fluid only boiled well after the rotor had been red hot (so around 1000 degrees celsius?) for quite some time. I've only ever gotten my rotor brown and my wife who has worse braking habits than me has gotten her rotors blue.
There's also the brake force one H2O brake system which uses a water and glycol mixture as fluid.