It doesn’t wheter I click Dark Mode or Light Mode, it remains with Whie and Green design
That’s weird. Seems the “dark theme” is the same as the light theme.
You can try changing the styles with a stylesheet editor extension, such as Stylebot for Chrome. Then, set the site CSS to this:
body, .menu-panel, .notifications *, .user-stream * {
background: #222;
color: #aaa;
}
a {
color: #eee;
}
.btn {
background: black;
color: #aaa;
}
.btn:hover {
color: #fff;
}
.main-nav a:hover, #navigation-bar a:hover, .d-header-icons a:hover {
color: #000;
}
.primary-textual, .topic-map {
background: #444;
}
#reply-control, #reply-control textarea, #reply-control input, .d-editor-button-bar {
background: black;
color: #aaa;
}
You can change the individual styles to get them how you like.