The color editor is UGLY
not sure what you mean by the colour editor. Can you post a screenshot to illustrate what you’re referring to?
Rereading your thread, I realise you’re probably referring to the HTML editor. This editor can be themed with your custom CSS file using the following filter,
add_filter('cf7sg_admin_editor_theme', 'load_html_theme');
function load_html_theme($handle){
return 'css/my-theme.css'; //make sure the file css/my-theme.css exists in the your theme folder.
}
You can download an existing theme of your choice from the CodeMirror site.