Dell's Ultrasharp monitors have very good colour replication. The
2408WFP is a very good screen. It uses a S-PVA LCD panel so the colour reproduction and viewing angle are very good and it is well within your budget at £383 +VAT.
There is a very in depth review of this monitor at
www.tftcentral.co.uk.
As with any screen unless it is calibrated the colour reproduction will be far from perfect but if your budget is £500 you can easily afford a cheap calibration device to go with it.