After a long discussion and confusion about the spelling of whether it is <gray> or <grey> at the dinner table, we had to “look it up.” <Gray> started in use in 1863 as the color the Southern troops of the US Civil War.
The distinction between the two spellings is defined by location. The US spells the color <gray>, while in Britain it is spelled <grey>. I think some of the confusion comes from the word <greyhound>, a specific dog bread. Although most greyhounds are not necessarily gray, it has created some confusion about how the word <gray> is spelled. <Greyhound> came from the word <grew> which is a middle English word for <Greek>. There is reference to a saying, using <grey>, that was used by the Old Norse in Iceland which almost sparked a war between the pagans and the Christians. In this saying <grey> referenced a derogatory term for a female dog.
So, if you are in the US, it might be especially important to spell the color between black and white with an <ay> at the end. You wouldn’t want to offend an Icelandic person, or anything. If you don’t know anyone who is Icelandic, you do now.