Gray is a indo-european word

gray (adj.) [etymonline]

"of a color between white and black; having little or no color or luminosity, Old English græg "gray" (Mercian grei), from Proto-Germanic *grewa- "gray" (source also of Old Norse grar, Old Frisian gre, Middle Dutch gra, Dutch graw, Old High German grao, German grau), with no certain connections outside Germanic. French gris, Spanish gris, Italian grigio, Medieval Latin griseus are Germanic loan-words. "

But the word gray is indo-european:

Polish szary:gray, Russian: серый :gray, Sanskrit: काल adj. kAla dark-blue.