Presented as a gift in 1848 to Thomas Francis Meagher from a small group of French women sympathetic to Irish nationalism,[3] it was intended to symbolise the inclusion and hoped-for union between Roman Catholics (symbolised by the green colour) and Protestants (symbolised by the orange colour).
If the Dutch had designed it, the protestants would have been on top, in 1848 we just lost half the country to the catholics in the south during a civil war AKA the Belgian revolution. If the Germans had designed it, I don’t think Germany was united as a country jet in 1848?
After browsing the “History of Germany” wikipedia page, I found the German Empire that popped in around 1848, which had the the same colors of the modern German flag.