For CSS, a great source for snippets is this Github repo or checking out this forum thread
For coloring text, you can use Deathau’s Notation Colour Blocks which will look in edit mode like:
``` note-purple
This text will be pruple
```\
or
<span class="purple"> This note will be purple </span>
Alternatively you can use the 8+8 highlight snippet to color highlighted, italicized or bolded text using tags
e.g.
#h/red **This bold text will be red**
#h/red ==This highlighted text will be highlighted red==
#h/red *This italicized text will be red*