Trevor,
1. You can check the current scope of text by placing the caret there plus pressing ctrl-shift-p. You will see that there are different selectors active in your examples.
2. With a version of brilliance black it looks like this:
I don't see your problem… the left two examples have embedded source code which is correctly marked up and has a blue background in MacClassic, black here. The right example has no embedded source and thus no blue.
??
Dan