How do I change the color of Semantic UI icons?

You can also apply: <i class="red users icon"></i> .For more information about semantic-ui I recommend to visit this doc http://semantic-ui.com/elements/icon.html#/definition

You can apply:

color: gray; // or any suitable color code, e.g. #808080

to one of the existing classes thumbs up icon large if suitable, or add a new class of your own and apply styling to this instead:

HTML

<i class="thumbs up icon large own-class"></i>

Stylesheet

.own-class {
    color: gray;
}