My understanding is that the meaning of 青 did not drift because of increasing western contact so much as abruptly change with a single cause:
But the real change came during the Allied occupation of Japan after World War II, when new educational material started to circulate. In 1951, teaching guidelines for first grade teachers distinguished blue from green, and the word midori was shoehorned to fit this new purpose.
The previous sentence in the source does talk about crayons in 1917, though.
My understanding is that the meaning of 青 did not drift because of increasing western contact so much as abruptly change with a single cause:
The previous sentence in the source does talk about crayons in 1917, though.