It is a myth that buying the premier color dell monitors at extra cost means you will get accurate colours right out of the box. It's not so simple. You need to calibrate the colours with respect to the lighting environment that your monitor is working in at the time of measurement, using a precision colorimeter. The moment someone switches on an extra light (whether it is a fluorescent, halogen, tungsten or LED light also matters) in the hallway or living room, the calibration may no longer be accurate, and thus the colour accuracy will also run.
Choosing the right color space for a particular usage also influences how the calibration benefits you. Most professionally done reviews of the dell monitors tell us that wide gamut monitors hardly ever come calibrated to be optimally accurate straight out of the box in Singapore. Maybe cos they were calibrated in different settings which are arbitrarily defined by Dell as "general purpose" to suit most users.