Many of the multicoloured notes underwent some minor colour changes. Many of the blue-green tones that you are referring to in the $1, $2, $20, $100 were reduced to create a more uniform colour across the note. Compare the early 2-letter notes to the later 3-letter or 11-digit notes and you will see clearly what I am referring to. I have no idea where the changeover might be, but sooner or later someone is going to research the topic to death and accumulate a massive collection of these notes, find about 40 discrete changeover points and publish a thesis on the subject. Eventually. So far, nobody seems to have cared, though many have noticed.
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BWJM, F.O.N.A.
Life Member of CPMS, RCNA, ONA, ANA, IBNS, WCS.
President, IBNS Ontario Chapter.
Treasurer, Waterloo Coin Society.
Show Chair, Cambridge Coin Show.
Fellow of the Ontario Numismatic Association.