Yorkshire’s Influence on Sweden

"Ej Upp" sign, Stockholm underground

I was confused by these signs. Surely “Ej upp” is a greeting? And if so, why is it in red with a “no entry” icon?

At the risk of detracting from what it supposed to be humour, some northern English dialect is actually descended from Scandinavia. Though whenever I see most of these comparison charts I don’t recognise half the words!