These too-cheap-to-be-true screens use TN panels that have just terrible viewing angles. I bought an HP 22" panel the other week and got rid of it almost immediately as the colours would shift as you moved your head.
Replaced it with a Dell 2408WFP instead which is 100x better, if significantly more expensive.
It's confusing as you'd think 2409 > 2408 but that's very far from the truth.