Why is my Header see-through?

It's OK! This is a common mistake we see made when the header colour is changed. It can be easily resolved by changing colour transparency in the Design panel.

When selecting a colour or background colour of a header, button and/or text from the Design Panel, the Colour Picker providers two sliders:

The first is a colour slider, which allows you to pick a colour from across the spectrum. Below that, is a transparency slider, which similarly allows you to adjust to the desired opacity, with the left being invisible and right completely solid.

Header Transparency

The Header Background gives you these same colour and transparency controls. If you notice your header is transparent, it's probably because the transparency slider is all the way to the left. Go back to the Design panel and ensure the transparency slider is put to the maximum value on the right.