I appreciate your concern on following the guidelines.
I disagree on the answers above that the guidelines are only to be referred and you could use your own sort of imagination. Although true, it discourages developers and motivates them to follow design patterns they might have not tested, thus causing an unexpected outcome.
Hence, it's always good to validate and check if there's something in the guidelines you could take inspiration from.
The Toolbar is the most iconic part of Material Design ever since ActionBar was deprecated.
Here are all colors and metrics you'll need to know to follow proper Material Design conventions for the Toolbar and the App bar:
No, you shouldn't highlight the bottom of the Toolbar with Accent Color line. That was somewhat followed in Kitkat design principle and has been abandoned ever since.
Now regardless of the Toolbar you select the one thing you definitely need to follow is to Elevate the toolbar. This happens on Z index, showcasing that the Toolbar is on top of the other elements and yet below Status bar and Nav bar.
To do this, in Android XML, for Toolbar use the following property.