Mr M. I am looking at the site and it is operating normally so the issue must be with the colour settings on your computer.

open Settings and go to Ease of Access. On the left, choose “Colour & high contrast.” On the right, you see the color filter that is selected as the default: Grayscale. Look for the switch that says “Apply color filter,” and turn it off.

if its not that I'm afraid it could be your graphics card is faulty