When there a fire extinguisher color code?

Silver is a water can (Class A) or a Class K for grease fryers. Red is ABC extinguishers (multi-purpose) and for CO extinguishers. Yellow is for Class D (flammable metals).

As for Fire Extinguisher LABEL colours, that depends on what they contain, which determines which type of fires each type may be used to extinguish, thus:

a) Red (Water/Gas originally) - for solid fuel (i.e.wood/paper), fires - though this colour has now been adopted for other extinguishers.

b) Blue (Dry Powder) - for Wheel/Brake fires on aircraft.

c) Cream (Foam) - for liquid/fuel fires.

d) Black (Carbon Dioxide gas) - for electrical or fuel fires.

e) Green (Bromoclorodiflouromethane, or BCF) - for fuel/electrical fires.

The green type is no longer available in the UK for civilian use.