How to add a class to comments that meet certain conditions

Hi, I’m new to plugin development, but I’ve been looking quite enough for an answer to my question, and can’t seem to find it.
The question is: how can I add a custom class, or maybe a wrapper with a class, to every comment that meets a certain condition, i. e. has a a certain meta key that my plugin assigns.
For example, lets say I want to add a class to every comment with the word “tree”. When the comment is inserted into the database, I check for the word “tree”, and if present, I add a meta key and value to to that comment (for example, “tree” => “true”). Now I want to add the class “tree” to all those comments (for example, the class “green”), so I can display those comments with a green background, for example.
I’ve been looking into comment_class(), get_comment_class() and other options, but nothing seems to fit.
Hope I’m clear enough. Thanks in advance!