What do you know today that you didn't know yesterday?

[Mister Agenda]

Originally, Isaac Newton divided the colours of the rainbow into not seven, but five colours: Red, Yellow, Green, Blue, Violet.

He added orange and indigo later out of a desire to match seven colours with seven notes on the diatonic scale. Presumably, it would take a while before anyone tried to take this to its logical 12TET conclusion and divided it into 12 colours.

Also of note, languages' understanding of colour tends to evolve in a surprisingly predictable manner.

1. Dark/cool, Light/warm colours
2. Red
3/4. Yellow and Green (Which one is first varies, but it's always one and then the other, never just skipping to the next stage)
5. Blue (Many languages don't reach this point until contact with another nation that has. Consequently, the word for "Blue" is frequently a loanword from another language.)
6. Brown
7. Purple, Pink, Orange, or Grey. (Notably, in English, "orange" wasn't really a thing until orange fruits reached Europe in the 15th century, and people decided that calling its colour "a yellowish red" didn't cut it.)

In addition, though foxes and tigers may have similar hues, tigers are generally considered orange, but foxes are more likely to be considered red because Europe knew about foxes long before we knew about the colour orange, but knowledge of tigers came after orange.

Let's add octarine, jale, and ulfire.