For many years the colour of the outer casing of portable fire extinguishers indicated the type of medium that they contained. The colours were normally; blue for powder, red for water, black for carbon dioxide, cream for foam and green for halon.

The specification for the colour coding were contained within British standards BS5423 (withdrawn in 1996) and guidance on the selection and installation of the extinguishers was included within British standards code of practice BS 5306 Part 3:2003.

During the 1990s, a European standard was drafted that replaced national standards. The series of standards were designated EN3 (and published in the UK as BS EN3) and this standard number can be found on most fire extinguishers that are sold today.

One requirement of EN3 is that the majority of the surface area of the body of all types of portable fire extinguishers is painted red, this makes type differentiation by colour more difficult. However, it does allow for an area between 3 and 5% of the surface area to be colour coded to indicate the extinguisher type BS7863 was drafted to give additional guidance on where this colour coded area should be placed on the extinguisher.

In 2000, the British standards institution revised BS 5306 Part3, splitting it into two parts i.e BS5306 Part 3 and Part 8 which now includes the advice on selection and installation. This states that extinguishers should, in most cases, be in accordance with BS EN3, by implication this recommendation requires the installation of predominantly red fire extinguishers.