Hi Danny,
You can do this (for tickets) through Styles. Right-click on any incident header and choose Configure All (or Personalize All, if you're on versions prior to Fuji). You should see a tab for the styles that relate to Incident. You can define what you need here by clicking "New" to add a new style to your Incident configuration.
In general, styles are stored in [sys_ui_style], and can be accessed using the Field Styles module under System UI on the navigator.
I'm not sure about color-coding the emails, I would assume some sort of CSS injected into your email body to apply the styles you need.
Thanks,
-Brian
