Ontario License Plate Sticker

The validation sticker that's attached to Ontario licence plates has always intrigued me. Particularly the choice of colours for text and background. Looking around at just a few cars there doesn't seem to be any pattern - except when two examples from the same year and month match. Then it becomes a question as to whether the colour scheme has some relationship to its expiration date. Let's assume it does. Is it consistent? Is there a pattern or does the ministry of transportation choose colours at random? Can one devise a method that predicts future sticker colours?

I've tried writing down colours as I encounter them. Ive started a few such lists but invariably I forget to bring one or lose them and have to start over. Even after a sizeable collection I still have many gaps. Finding stickers that hit enough of the dates required, densely, seem almost impossible.

Fortunately others have made websites that summarize sticker colours for well over 25 years worth of stickers.

It comes down to a total of five colours used either for text or for background.
They are: white, black, red, green, blue, magenta.
Of course the text and background must be different colours. One of them must be white.
That makes a total of ten combinations.

The sticker's expiry months are grouped together into four groups. Jan/Feb/Mar, Apr/May/Jun, Jul/Aug/Sep, and Oct/Nov/Dec.

For example, stickers that expire in January vs. March will share the same colours.

Below is a table that shows all possible colour combinations and how they are picked via year (last digit) and month.

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Given a complete table I now wanted to find a formula that can determine colours from the year and month. Hopefully a formula that's simple enough to do in one's head, just for fun, when looking at stickers.

It turns out the formula isn't simple and the colours are not easily remembered as there are many combinations.

Because a person's birthdate doesn't change, they may only ever encounter from three to five out of the possible ten colour combinations.

If they renew the sticker every year or every two years consistently then the colours will cycle through all five available combinations.

If stickers are bought in 1 / 2 / 2 year increments they will encounter only three.

To use the tool click the link at the top of this page.

Revised 6 Nov 2018