Parallax Section / HTML in content

I am having troubles setting a semitransparent background behind my text in a parallax section.
If I use: <p style=“background-color:blue;”> it works perfectly and my text gets a blue background. However once I change the tag to “background-color:rgb(0,0,255);opacity:0.6;” it just disappears. The same goes when I use rgba or hsla.

Unfortunately I do not understand enough about HTML and CSS to figure out the problem.

Hey there

Xoph, can you show me your problem? please provide a link to the page and screenshot of the problem would be also very good