Edit: Pheck me, I'm way to slow to respond. 2 pages went while i was playing Xenoblade.I was actually confused before - I thought you were talking about this https://www.theguardian.com/world/2015/sep/17/madrid-ends-blacking-up-post-christmas-tradition not Spanish Holy Week.
But here it shows that the city of Madrid back in 2015 (Griezmann was in Madrid in 2015, no?) ended the process of having someone blacken up at the Three Kings Parade as they quite rightly realised it was racist. So Griezmann can't solely lay blame on not being from the US.
But I agree that I don't think Griezmann is a racist, just an idiot.

I'm sure there is tons of stuff Norway has changed policies on that I haven't kept updated with for some reason.
The idea that just because he played football in Madrid he'd know about such a change or the history behind it is jumping the gun.
Naturally, it does mean it's not impossible that he'd be aware of it, but likely or unlikely is hard to determine from that alone.
Found this statement from Griezmann in Norwegian medias:
"– Jeg innrømmer at det var klønete gjort av meg. Dersom jeg såret noen, så beklager jeg, sa han før han slettet tweeten om Globetrotters, og det opprinnelige bildet."
Roughly translated to "I admit that what i did wasn't thought through. Sorry if I hurt anyone." and that he deleted the picture.