English is full of interesting words. For example, the popular shade of blue known as turquoise comes from a French term that means “Turkish stone.” Some thought incorrectly that these stones all came from Turkey. While turquoise was in fact traded in Turkey, the true origin of these bluish gems was probably Iran or the Sinai Peninsula. The turquoise that first came in Europe was most likely obtained in Turkey by Venetian traders.
Another possibility for this shade’s association with Turkey is reputation of the Sultan Ahmed Mosque in Istanbul. Its walls are decorated with so many blue tiles it’s known as the Blue Mosque.
A good explanation is at http://www.turquoiseguide.com/articles/turquoise/turquoise-basics/name.htm
The Sultan Ahmed Mosque is described at https://en.wikipedia.org/wiki/Sultan_Ahmed_Mosque