Backround color turns white when loading page

My theme has a black bachround color to match the rest of my site. However the backround color on all wordpress pages, blogs etc. turns white while loading the page. Than a few seconds latter turns black again.

Is this normal? Can it be fixed? Its not really a huge issue, just kinda annoying.

See my photoblog to see what i mean:
https://capedmaskedandarmed.com/photoblog