Turkey; Türkiye
Refers to the country Turkey. The form トルコ is standard; the ateji forms are historical and rarely seen.
from Portuguese Turco
I plan to travel to Turkey next year.
Abbreviation used in compound words like トルコ石 (turquoise stone) or トルコブルー (turquoise blue). Not used as a standalone word for the color or gem in modern Japanese.
I like turquoise accessories.
This wall color is called turquoise blue.