Hello Shashank.

Go into Tools > Options > Content and make sure that "Load images automatically" is checked and that the sites you want images to be shown in are not exceptions (click Exceptions to check).

In the same scree, click Colors... and make sure "allow pages to load their own colors" is ticked.

If that doesn't work, you may be having a problem with some extension or plugin that is hindering your Firefox's normal behavior. Have you tried disabling all add-ons (just to check), to see if Firefox goes back to normal?

See also: Website colors are wrong Websites look wrong or appear differently than they should