Blue marks

The blue marks that are visible on the surface of the screen, visible in the conditions that you describe, are synonymous of marks caused by the naturally occurring oils from your skin/fingers. Having ensured that the screen is free of potentially abrasive dust - a dry microfibre cloth will usually remove any oil-marks from the oleophobic coating of the screen.

Additional advice from cleaning your Apple devices can be found here:

How to clean your Apple products – Apple Support

Hello Pranay:

You have determine the source of those blue marks on the screen of our iPad. Are they smudge marks or do you believe that it is internal? Can you post a screenshot if possible?

Axel F.