Evolution of human colour vision lights, which appear to be clear. Other colour perception issues include having trouble distinguishing yellows from reds and violet, lavender and purple from blue. In other cases, objects that reflect both red and blue light may appear to just be blue to these individuals. Deuteranopes, who are missing medium wavelength sensitive cones, are similar to protanopes in that they cannot distinguish between colours in the green-yellow-red part of the electromagnetic spectrum. However, deuteranopes do not suffer from dimming issues. For example, purple colors are not seen as being opposite to other colours in the spectrum but instead appear to be
Trooping the Colour (and, once they have collected their colour during the ceremony, as 'Escort to the Colour'). At the outset, the colour is held by the Colour Party - a colour sergeant and two other guardsmen of No. 1 Guards, standing well-spaced on the northern side of Horse Guards Parade. Once obtained by the Regimental Sergeant Major of No. 1 Guard, the colour is borne through the ranks of Nos 2-6 Guards by an Ensign of No. 1 Guard. It is a great honour for a young officer to carry the colour in this ceremony, as historically only the most courageous Ensigns