Industrial standard is D50, or 5000k.
But nowadays it's relatively safe to calibrate anywhere between 5000k and 6500k.
problem with 6500k will be a slightly warmer print result if you're gonna outsource your printing to pro printing houses.
winson can help to verify on this?
I belonged to the old school of users with knowledge on CRT (tube) and prints (CMYK). Todays flat-panel LCD monitors are very affordable and good. Hence, most of us do not talk about temperature, gamma, etc. Most of us dont even bother to calibrate unless theres a need to do image retouching, this source of work or income had been render obsolete with files supplied ready to print. Colour-separation and colour retouching as a trade is dead. In a printing environment, most of the lights are florescent tube, around 2500K to 3500K. The only light at the press or viewing table is 5000K, or we call it daylight.
If you are into video or want to watch a movie with your monitor, you can set to 6500K to 9300K. Images are bluer and brighter.
But if you were going to prints, I would recommend a white point of 5000K with a gamma of 2.2. If you have been viewing uncalibrated display, your initial reaction upon performing your first monitor calibration will likely be, Oops!
.. what did I do wrong?. Does it make sense to calibrate a monitor to have a dull screen? If you are doing it correctly, a properly calibrated LCD display will look dark and flat with a rather warm colour balance. Im been conservative and realistic, as everyone expect to have prints like what they would see on their monitors. RGB vs CMYK.
There are two camps...6500K and 5000K, bluer or cooler and yellower or warmer. Those using the latter are mainly concerned with matching prints that they're viewing under a 5000K viewing box.
I wound not recommend 6500K to photographers. My sense is that he is not working in a fully profiled environment and is still relying on last minute visual tweaks to match.
Anyway, you have the freedom to decide what setting works for you, but remember: don't expect the colours you match and edited under your "6500K colour calibrated screen" to behave the same way in the rest of the world which are closer to 5000 K than 6500 K. Be careful with your suppliers, clients and people like me.