* γκρι (gri): This is a loanword from French ("gris") and is the most common and straightforward way to say "gray" in modern Greek.
* γλαυκός (glaukós): This word traditionally means "grayish-blue" or "blue-gray," often used to describe the color of the sea or eyes. It wouldn't be appropriate for all shades of gray.
* You could also use descriptive phrases depending on the shade, such as αχνό (achnó) for a light gray (like mist) or a combination of words to describe a specific shade (e.g., σκούρο γκρι (skouro gri) for "dark gray").
Therefore, γκρι (gri) is generally the best and easiest option.