Had this problem about a year ago (aything blue was a weird purple!) - drove me nuts! Try this (since I read you're displaying "Working CMYK" - and monitors display RGB): View>Proof Setup>Custom -under Proof Conditions: Device to Simulate - choose your monitor (believe it or not, the model number/designation should be in the giant list of options in the pulldown menu). Hope that helps. Good luck- -Lew ;-)