Additional notes in README.

README.md

@@ -139,17 +139,17 @@ plugins:
 The plugin will insert the correct call to the javascript library
 inside the final HTML page.
 
-### Use of the Material theme
+### Additional settings for the Material theme
 
-!!! Note
- The [Material theme](https://squidfunk.github.io/mkdocs-material/), 
- developed by [squidfunk](https:/squidfunk)
- is not mandatory, but recommended.
 
- **Mermaid diagrams will automatically adapt their colors to the theme
- and palette.**
+> The [Material theme](https://squidfunk.github.io/mkdocs-material/), 
+> developed by [squidfunk](https:/squidfunk)
+> is not mandatory, but recommended.
 
-Here are the recommended settings in the configuration file:
+**Mermaid diagrams will automatically adapt their colors to the theme
+and palette.**
+
+Here are the _additional_ recommended settings in the configuration file:
 
 ```yaml
 markdown_extensions:
@@ -162,6 +162,9 @@ markdown_extensions:
 
 ```
 
+> Do not use these additional settings for other themes, 
+> as diagrams will probably **not** be displayed correctly. 
+
 
 ## For more information
 See the [documentation on ReadTheDocs](https://mkdocs-mermaid2.readthedocs.io).