The terms gray and grey are two different spellings of the same word which refers to “a color intermediate between black and white, as of ashes or an overcast sky.” Some people become confused due to the one-letter spelling difference but they actually mean the same thing.
Examples of the use of gray as a color:
“Do You See Gray Or Blue In The Vegas Golden Knights Logo?”
Deadspin“10 gray items that rock fall color”
Chicago Tribune“Canon EOS Rebel T6 with gray design quietly launched in U.S.”
SlashGear
Examples of grey as a color:
“Grey end to this dark year”
The Guardian“Genius ways to hide your grey hair”
Times of India“adidas Unveils the Ultra Boost 3.0 in Grey and White”
Highsnobiety
They may also be used to mean “dull and nondescript; without interest or character.”
“Some Snow on This Gray, Gloomy Thanksgiving”
NECN“The Cats, from days of grey to days of glory”
Canberra Times“Feeling Grey About Fifty Shades”
Huffington Post
The spelling difference may be observed as a result of preference. Gray is the more popular spelling in American English while grey is predominantly used in British and Canadian English. Both terms originated from the old English word grǣg.
Both grey and gray can also be used as a verb which means “to become gray with age.”
“Graying of rural Nebraska changing the landscape of agriculture”
NTV“Going back to his roots! Silver fox Colin Farrell reveals drastically greying hair as he touches down in Los Angeles”
Daily Mail“Texas is Graying and the State Needs to Adapt to It”
UT News
When writing, you need to take note of the reading audience in order to decide whether to use gray or grey. An easy way to remember which term to use is that gray with an “a” is for Americans and grey with an “e” is for people in England.