Facing colour engineers and support corps normally had a single branch colour, although exceptionally each regiment of Swedish artillery had its own facing colour until 1910. The United States regular army after the American Civil War adopted a universal dark and light blue uniform under which each regiment was distinguished only by numbers and other insignia, plus branch colors. The latter were yellow for Cavalry, red for Artillery and white (later light blue) for infantry. Combinations of colors such as scarlet piped with white for Engineers, orange piped with white for the Signal Corps and black piped with scarlet for Ordnance personnel
Colour centre cannot track the actual firing of neurons, which happen on a millisecond timescale, but it can track the haemodynamic response, which happens on a seconds timescale. This method is ideal for tracking colour selective neurons because colour perception results in a visual after-image that can be observed in the neurons, which lasts about 15 seconds. Sakai et al. used fMRI to observe whether activation of the fusiform gyrus correlated with the perception of colour and the after image. The subjects in the Sakai study were placed in the fMRI machine and were subsequently subjected to various visual stimuli. A series