color header media changes automatically

Hi Skandha, I made a picture 1920 x 822 px for the header media. This picture contains a lot of white. After placing this picture in the header media, the color white turns into a kind of grey color. And that isn’t what I thought that should happen. Next thing was making a completely red picture with the samen measurements. After placing this in the header media, the result was perfect. Next step: making a completely white picture with the samen measurements. Result: a grey header media. You can see this at: Laura.hagmeijer.nl Can you please provide me with a solution so that the header media stays white? Kind regards Hans Hagmeijer