The cleanest way to do it in my opinion is a SSX. You could also use the Advanced->@lessCode property of your current color theme. You’ll need to use CSS (or LESS) to implement your custom styles.
Pretty much any introduction to CSS + the link I shared with you above.
I don’t think so, your problem is not about the content generated but about how it’s showed to the users. Similarly to the previous problem, in my opinion you should fix that with CSS rules.