ViewSonic external monitor appears yellow when connected to iMac

Hi,

I have a 24 inch imac and i am connecting the viewsonic VG921m (19'') monitor using the mini-dvi port.
The external monitor appears dull (whites have a yellow tint)
Is there a way to match up the display to look like mac?
I am using the monitor next to my iMac and its currently distracting as its displaying same colors in different tone.

Any help is highly appreciated!

Thanks
Devang Kamdar