Frank
I have seen them mixing up one or all the tyres (often communication error there probably) for a pit stop several times, both wrong compound and the ones from the wrong driver. Though usually someone notices it and it just causes some delay. At least current compounds are clearly different looking, once they remove the heating jackets that is. But that's happening even to the really highly trained guys, albeit under pressure, not just some Pirelli logistics dude in a factory or warehouse in Turkey or Great Britain. It also happened that some mechanic forgot to put some piece into the car, or tighten an important screw properly, without someone else noticing afterwards, so a mismatched tyre might escape their attention too.
Like what happened to Bottas, at the 2015 Belgian GP, when the Williams Martini mechanics fitted 3
SOFT and 1 MEDIUM tyre