Hikvision DS-7604NI-E1 Camera Access

Hi, I currently have a couple of Cameras connected to DS-7604NI-E1 and the cameras were using night vision at night, recently they have turned to colour only and I cant seem to find a setting anywhere which can set DAY/Night mode..?
Any Ideas?
I also tried setting Virtual host but it looks like this isnt supported on this NVR?
Any help will be appreciated.
Thanks