Dell U2410 HDMI + OS X Lion very poor quality

The problem was caused by OS X outputting in YPbPr not RGB. YPbPr sends approximate colours and is used primarily for TVs. Unlike Windows, OS X didn't recognise the Dell as a Monitor because of the HDMI connection. Shifting to a DVI connector fixed this and forced RGB colour data, and thus, correct colours.

So no, it was not a problem with callibrating the monitor or its colour profile

I joined just for saving anyone interested from the frustration I had in the last couple of hours. This fixed it for me (the universal patch).

On your U2410, set Display Settings -> Sharpness to 0 then everything will be fine.

I use Macbook Air 13' 2011 mid with Moshi HDMI connector.

While I use DisplayPort to connect, no configuration needed. So it may be some bug with dell monitors.