Colo(u)r printouts on IP4000

My IP4000 prints out a muddy colour instead of green/blue when I print
directly from the computer (MacOSX). If I print from Photoshop the colours
are correct. I've messed about with Colorsync without any success. I've
re-installed the latest driver but it made no difference. The cartridges are
almost full and the nozzle printout is clear. Anyone suggest a solution,
please?
Incidentally my HP prints in proper colours the items that Canon messes up!
So - why not use the HP? Because I like the duplex function.
Ken

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