Where did you read that prison labour is common in Europe?

https://en.wikipedia.org/wiki/Paid_prison_labour

The availability of paid work in Europe is increasingly low. For instance, approximately only 5,300 labour roles are offered to 12,500 prisoners in Greece, while in Italy there is only one inmate out of five who is entitled to paid work.[21]

And before you nitpick. Unpaid work (like helping in the kitchen) translates into reduced sentences and isn't common at all.

It also doesn't matter what colour their skin is.