How to set default screen resolution and color depth without monitor in windows 7

First set desired resolution using:

ControlPanel → Display → Screen Resolution.

Also set ColorDepth using:

ControlPanel→ Display → Screen Resolution → Advance Settings → Monitor → Color

After this in regedit, manually search for DefaultSettings.XResolution, DefaultSettings.YResolution and BitsPerPixel and change all those to 1920, 1200, 16 (All in Decimal) respectively using next search button F3.
I also added entry of ColorDepth for RDP connection(not mandatory)::

[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services] "ColorDepth"=dword:00000003 in decimal.

I don't know, which portion of registry did this, but now it works.