My monitor at work is the same way - the difference should be very slight, but if you need to make it more, you probably want to try to increase the contrast while also increasing the brightness. It may also be a gamma problem. If you get close I think that is good enough.
Michael, the only problem I am detecting is an inability to distinguish between the last two columns on the right, for any colour (apart from maybe the yellow, where there is a very faint difference) and also the black.
Any idea why that would be and what I should do to fix?