Evolution of human colour vision that are found between 450 and 625. Individuals with various forms of colour blindness such as deuteranopia and protanopia are missing human middle wavelength sensitive or long wavelength sensitive opsins. Their minimum wavelength differences are <5 but only at around 500. Protanopes, who are missing long wavelength sensitive cones, are unable to distinguish between colours in the green-yellow-red section of the electromagnetic spectrum. They find yellow, red and orange colours to have much lower brightness when compared to a trichromat. The dimming of these colours can result in confusion in many cases, such as when attempting to identify red traffic
Unit Colour Patch was assigned a colour and the Brigade HQ colour patches were the Divisional shape in the Brigade colour. Each Battalion in each Brigade was then assigned a colour, and the patch was split horizontally with the Battalion colour across the top of the field and the Brigade across the bottom of the field. Light Horse, Artillery, Engineer and Medical units were also allocated colour patches. Light Horse patches were divided diagonally. In total over 300 individual patches were authorized during the war. Military Order 206/21 in 1921 authorised the use of Unit Colour Patches for the Citizen Military Forces (CMF),