In this very very very short tutorial I will show you how to make your backgrounds transparent. Similar to the picture below.
You might have noticed that there is no rgba settings with in PL5.
But that doesn't exactly mean you cant use rgba.
To make use of rgba navigate to the background options and you will have to enter the rgba values manually. For example:
rgba(215, 44, 44, 0.5)
Is what you would add in the background box. See image below:
And there you have it.
If you have any questions post them in the comments below.