In addition to the comments about calibration, etc, I'd say that those are further off than most calibration problems would indicate.
Check your color space. Probably they want sRGB, you may well be operating in Adobe 1998.
If this were coming off of your printer, I'd say that you had the wrong profile or were managing color in the wrong place, but since these are from an outside service I don't know what the corresponding concepts would be.
_____ Brian... a bicoastal Nikonian and Team Member
My gallery is online. Comments and critique welcomed any time!