You might have better luck asking in /r/vexillology, which is all about flags.
The two main colours of British ensigns are the ones you've listed: red and blue. There are also green and white ensigns, but the Green is a now defunct ensign associated with Irish vessels and the White is for naval vessels and appears only on the flag of the British Antarctic Territory.
The Red, Blue, and White Ensigns were associated with different squadrons in the Royal Navy until 1864, when each was assigned to a different category of naval vessels. The White ensign was assigned to military vessels, the Blue was given to vessels employed by public offices, and the Red to everything else.
I haven't been able to find any conclusive evidence, but this 1864 divide would likely determine the general time period where a colonial flag could be either red or blue. Canada, which was settled and developed long before 1864 received a Red Ensign. The same goes for the United States, South Africa, and others.
Because the Blue Ensign was adopted by any publicly-employed vessels this would have included colonial authorities who established colonies flying ensigns chosen under the post-1864 guidelines. It makes sense that new colonies would adopt a flag based on the flags flown by colonial authorities.
However, there is not a perfect divide between red pre-1864 and blue post-1864. Australia was settled before 1864 and, although paintings depict the settling ships as flying Red Ensigns the modern flag is now blue. While Australia also has a Red Ensign that can be flown, historically it's flag has shifted between designs that incorporated both colours. The same goes for New Zealand. Overseas Territories that were colonised before 1864 use the post-1864 guidelines and have predominantly Blue Ensigns as they are still administered by British public offices.
I understand this is not the most definitive answer but the topic is far more complex than it seems. Hopefully /r/vexillology or someone more versed in this subject than I can help to fill in the huge gaps.
http://www.luxe-motor-kei.co.uk/documents/NavalFlagsandEnsigns.pdf