Here's pic of my new MYBB forum after changing global.css. I entered a color code #4F1AAB where you see #000000 then changed it back and you can see the results.
I Have NO IDEA what happened or what to do next
Have you tried resetting or re-uploading the theme?
I've been using MYBB for about an hour and only have the default theme. How would I 'reset' it? Or perhaps I should upload another thee and start again?
Could you tell us your url?
It's looks like your board url option is not the same as your real board url, test that!
CHMOD the ./cache/ and ./cache/themes directories to 777.
..and here's the URL setting
Yes all CHMOD's completed, cache and cache/themes both 777 and the BB showed perfect for about 30 minutes.
Here's a pic of the permissions in Smart FTP. Is this what you wanted to make sure of?
I have changed ALL of the cache and cache/theme related folders to 777, still no change.