WP File Manager

Name	Action
..
index.html	Edit
javascript.css	Edit
javascript.js	Edit

Editing: javascript.css

span.js-keyword {color: #90b;} span.js-atom {color: #291;} span.js-variabledef {color: #00f;} span.js-localvariable {color: #049;} span.js-comment {color: #a70;} span.js-string {color: #a22;}