The only difference between this page's code and that of my basic Bootstrap example is the added background color on the container DIV here. See the Bootstrap background color classes. The color class here is bg-info and the opacity class is bg-opacity-25 (see opacity examples).
I have also increased the padding on all four sides of the container by adding the class p-4.
<div class="container mt-5 bg-info bg-opacity-25 p-4">
Resize your browser window to see how the container behaves at different widths.
The code underlying this page is a copy of the Bootstrap "getting started" example using CDN links. See the example.
There is one important addition: I have added a DIV element with the Bootstrap container class applied to it. This DIV contains everything visible on the page. In the same DIV, I also included the mt-5 class to add some space at the top of the container. Without that, the heading is too close to the top of the browser window, and it looks stupid. See the Bootstrap margin classes here.
This page does not include any Bootstrap rows or columns.