Jamaica (Proposal, 1962)
A flag contest was launched in Jamaica as the country was gearing up for independence in 1961. The winning design was chosen on 6 June 1962 and submitted to the British Admiralty Office for approval. But the Admiralty rejected it for being too similar to the flag of newly-independent Tanganyika. The parliamentary committee tasked with choosing the flag rearranged the colours of the rejected design into a new pattern, creating the modern Jamaican flag.
I’m glad Jamaica ended up with the flag it has, but I wonder if the Admiralty would have been so quick to reject this proposal if they had known that Tanganyika was going to disappear within the next two years.