Actually there is not a whole lot of evidence for what color tunics the Romans used, and the commonly accepted notion that they wore red is heavily debated. What little evidence there is might suggest that white or off-white might have been more commonly worn than red. In mosaics soldiers were more often depicted as wearing white than red.
Blue might have been used as well. There is a tombstone with an engraved image of the Optio it was erected for, that apparently had traces of blue paint on the tunic. It is also believed that the Roman navy might have worn blue tunics.
What are some good sources on this subject? I have a book that illustrates the Highland regiments of the 19th Century in some detail, but I have less information available on other units in the British Army of this period.
I've seen illustrations of the British soldiers in New Zealand (during the Maori Wars) wearing blue uniforms, yet elsewhere I see Victorian soldiers depicted in khaki uniforms or as 'redcoats' - what was the significance of the blue uniform? Was it for naval units, or was it used solely by the units in New Zealand?
It is a popular, but unsubstantiated assumption that during the New Zealand Wars of the 1860s, blue frocks were chosen because they offered better camouflage than the redcoats worn at the time. I am not sure where this originated, but it was obviously from someone with little knowledge of the subject.
No documentation has, to my knowledge, been found explaining the actual reasons. However, there are a few issues that warrant consideration in this matter.
1. At this stage, the British soldier was not wearing bright scarlet, but rather, the earlier brick red. It has sometimes been described as dirty red. Indeed, as it gets worn and dirty, it offers every bit as good a concealment as blue would in a forest, if not better. Whitened buff leather would actually be a bigger issue for concealment, standing out, as it does on both red or blue. So no. Camouflage or concealment was not the purpose.
2. The British soldier of the time had two basic items of dress. His Tunic and his Shell Jacket. Essentially, his tunic was his dress uniform and his shell was used for undress. In NZ, on the other side of the world and with issues of new tunics not being logistically easy, units would tend to keep their Tunics for formal occasions. This left the shell. Indeed, in the 1st NZ Wars of the 1840s, the shell appears to be the most common item of clothing used on campaign. There is evidence that in the early part of the 1860s, shells were still used in the field in NZ, albeit, sometimes worn under a privately sourced blue frock. However, again, as it wore out, the shell was not easy to replace. Also, in the often quite cold forests of NZ, shell jackets did not offer the soldier the best of coverage, especially to the lower back and kidneys. There is some evidence that again, in the early stages of the 1850s, some units may have cut down their greatcoats, so as to offer better protection and warmth to the body. With this in mind, some sort of frock coat would seem the logical substitute, affording the necessary coverage. Indeed, the India Frock has come into use at the time of The Mutiny and some units had brought their own versions of this garment to NZ. There are photos of the red India frocks being worn in NZ and at least one example survives. The India frock offers a basic pattern for the blue frocks seen in NZ.
3. At this stage, blue was a popular colour with colonial volunteers and police units. It would appear that vast amounts of blue serge were available in Australia/New Zealand. Indeed, contracts for the supply of blue serge uniforms for NZ Units were awarded in Australia to companies like C.K. Moore. So blue serge was therefore, likely cheap and plentiful.
Therefore, based on the points above and the research I have conducted into the matter, I am of the opinion that the adoption of blue serge frocks was to provide a cheap, serviceable uniform in the field, thereby preserving the tunic and shell jackets, the re-supply of which was made difficult and costly, with being on the other side of the world.