Where is a good place to learn about ImageMagick?
 

Specifically, about its features to add text and color blocks to static images for .php output?

Here's a couple of options...

1) Post in their Github Community. You might get a quick answer there.
2) Watch some of the YouTube Tutorials out there.
3) Here is one online tutorial and here is another that might help.

Hope you can get it resolved!

man convert