When I am searching the colour of $\ce{Mg3N2}$ I came across photos showing different colours: **greenish-yellow** on [Wikimedia](https://upload.wikimedia.org/wikipedia/commons/7/7b/Magnesium_nitride.jpg),
and some other **just yellow** on [some Google Images results](https://www.google.com/search?tbm=isch&q=magnesium+nitride).

I am eager to know what causes some samples to be bit greenish.