Red Heat

Red Heat is a 1988 American buddy cop action film directed by Walter Hill. The film stars Arnold Schwarzenegger, as Moscow narc Ivan Danko, and James Belushi, as Chicago detective Art Ridzik. Finding themselves on the same case, Danko and Ridzik work as partners to catch a cunning and deadly Soviet Georgian drug kingpin, Viktor Rostavili (Ed O'Ross), who also happens to be the killer of Danko's previous partner back in Soviet Russia.

The practice of using colours to determine the temperature of a piece of (usually) ferrous metal comes from blacksmithing. Long before thermometers were widely available it was necessary to know what state the metal was in for heat treating it and the only way to do this was to heat it up to a colour which was known to be best for the work.