nth-child – Post Titles

I have a custom post type that displays 3 items on the homepage:
The loop is layed out like this:
`<div>
<h3>Title Here</h3>
<p>Couple sentences here</p>
</div>
‘
What I’d like to do is change each ‘<h3>’ to a different color in each Post.
The first thing that came to mind is to use ‘nth-child’, but I can’t seem to get it to work.

I figure if this doesn’t work I could target the Post ID, but I’m still not clear on how to target that via CSS.

Any suggestions are appreciated
Thanks in advance