NEED CSS HELP!

I am trying to work with CSS for a game I'm uploading, and it's proving to be jarring considering I suck at coding and have never messed with CSS before. Basically, I'd like to make it where the boxes containing the messages are slightly transparent so that the background can be seen. Also, how to change font color? No, seriously, I'm having a lot of trouble with this. Google searches aren't helping me out since there seems to be many different versions of CSS.