Color laser M451dw grey is wrong

We just changed the black cartridge (CE410X) on our HP M451dw and now the primary user swears that printing color images in black and white produces grays that seem off. To my eye they appear somewhat green. All colors print quite nicely including black. The black print in the document in question is fine. Black prints fine in black and white as well as color. Colors print fine in color. Grey looks, almost olive drab in black and white. Any ideas before I suggest swapping out the black cartridge?

Thanks,

Warren