Add coloured 'boxes' to enclose content

[IsaacWoods]

Basically, you should be able to add a box of any colour (with a premade palette of good colours, pastel tones would work best I think), and then that box should be able to contain any content the rest of the document can. This would be a good way to enclose bits of content.

Thinking it'd be best to have a thin border that is a darker version of the box's colour.