[Shoredicth] Page background opacity

My theme, Shoreditch, uses the featured image as background on a specific page. I want the background to be a colour, and have therefore uploaded a square made in photoshop with the color added.

When it shows it seems like there is some kind of opacity added. The colors doesn no longer match the colorcode.

I can’t find the CSS which does this. Can anyone help?

The page URL is https://www.barnerettighetsdagen.no/test/ and to show the issue I have uploaded a background in the first page (with the header “Velkommen”). The picture uploaded has the same color as the header color, but as you can see that is changed when it is added as a featured image/background.