The "HINT" is in the word "è" (is). If "L'elefante" was plural, the "è" (is) would be "sono" (are). So, to recap, L'elefante è grigio singular BUT Gli elefanti sono grigie = plural. I hope that helps. The funny thing is, even with me supposedly knowing the above, I still responded incorrectly! DON'T GIVE UP!!
That's not what she said. http://www.imdb.com/title/tt0526716/quotes?qt=qt0242660
l'elefante--- singular and masculine use o grigio gli elefanti--- plural and masculine use i grigi
the gray woman- le donne grigie -fem, plural
I think the difficulty is with the e ending. It can be an ending for masculine, feminine and feminine plural. I have found that I just need to have repeated exposure to words that end in e. Then it starts to get easier.
Eventually, Your mind pays more attention to the article which helps you realize if the word is masculine, feminine or feminine plural. This lesson follows the lesson on possessives, perhaps that lesson caused your mind to try to match endings. But even then it would be il mio elefante grigio.
I responded to your answer to help myself better grasp the concept. Hopefully, I have brought clarity and not confusion. :)
Grey must be accepted. Here's Miriam Webster quote: Gray and grey are both common spellings of the color between black and white. Gray is more frequent in American English, whereas grey is more common in British English. The varying usage of both grey and gray extends to specialized terms such as animal species (gray/grey whale) and scientific terms (gray/grey matter). Greyhound is an exception, which has a different derivation than the color.