Desktop Screen is looking silver color for about 10-15 mins

Hi all,
1 month back, I purchased a new Lenovo C540 – 6267, 23", 4 GB RAM, 1 TB HDD and 2.9 GHz Pentium Processor. It is actually working very well.
But the problem with this is that sometimes it looks like the silver color for about 10-15 minutes. After 15 minutes of time it is coming to normal. All my video drivers are Up-to-date. I am now using Windows 7. Even when the system is fully charged it is showing like that only.
Is this problem related to Windows 7 OS or hardware related? Can somebody help me to figure out what is the issue? Thanks in advance for your kind help.
