The 8750 gives you the option of printing with black and gray inks only by selecting, I think, 'grayscale' in the printer driver. So, unless you want a deliberate tint, or a coloured feature in an otherwise b&w image, selecting this will dispense with any colour casts you might be experiencing. That said, my experience with a custom rgb profile on a similar model, the HP 7960, was that the driver and profile were substantially linear/neutral and gave lovely b&w prints. One last suggestion, starting with an image in aRGB colour space makes the profile work harder and can introduce larger conversion errors that show up as small colour casts. I have found that you can get a more neutral b&w by first converting a copy of your image to a smaller RGB space, such as sRGB, before printing. Regards,
Gary.