Watermark on 10.1" LCD display - How to Remove?

I’ve attached a file of a pic that shows a colored watermark at the top-right corner of this screen. This watermark does not disapear during use, anyone know how to get rid of it?
Adafruit watermark.jpg.jpg

As per the following Raspberry Pi Forum post, it is caused by using inadequately rated power supply.

Thanks and Warm Regards