If you want to use an emoji (like ❎) but don't want it to be green you can use the variation selector (0xFE0E)to change it to the text representation.
Use it in CSS like this:
.myClassName::after { content: \274E\FE0E; }
which will look like this ❎︎

Some emojis don't have a text representation.
To check what the text version looks like (if one exists) for any given character, go here and enter a utf-16 string (like 274E) or the character itself (❎). This is a very crude tool. Don't expect much.