Sometimes it can be such fun to yank soldiers' chains. ;D
If you were to measure the wavelength of the light reflected off of an armoured soldier's beret and compare it to that of a sailor's beret (this is how colour is actually defined), you would likely come up with the same result (after making allowances for grease, dust and wear
![Wink ;) ;)](https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f609.png)
). So yes,
technically, they are the same colour. Nevertheless, the soldier's is black and the sailor's is blue.
Ever since the Royal Navy standardized its uniforms in the mid-19th Century, their and (except for the green interlude) our uniforms have been the same colour. The colour has not changed. They have always been blue, because we say they are blue, notwithstanding the wavelength of the light reflected off of them. No sailor would ever wear a black uniform!
The history behind this is simple. Years ago (more than a century in fact), it was very difficult to attain consistency in blue dyes. Different batches of material would be slightly different shades and so uniformity would be lost. The solution to get around this was to make the dye very very dark. Dark to the point where a soldier (there were no air people then) would probably say it was black. In this way, consistency was obtained.
Back in the "Green" era, the Naval Officers Association of Canada sprung for the cost of traditional "blue" uniforms for the Stadacona and Naden Bands. The results were less than ideal. Unfortunately, no one told the tailors (they were all custom made) about the reality of "navy blue" and so they made the uniforms out of what the civilian world calls navy blue material. At inside venues, the uniforms looked great (although sailors don't wear black, they really shouldn't be wearing green). Alas, outside in the bright sunlight, they turned purple (not so good). We all got a bit of a chuckle out of that.
Thus in order to ensure our uniforms are blue, we have to dye them so dark that other folks think they are black, but they are blue nonetheless.
This debate reminds me of a similar one that went on for years in the Air Force. When the RAF was formed in 1918, it was an amalgamation of the Royal Flying Corps and the Royal Naval Air Service. A new badge with a "bird" was designed and issued. For years the debate went on as to what kind of bird it was. Despite an official description calling it an eagle, the RNAS veterans swore up and down that it was an albatross and you could never convince them differently.