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<div ng-app>
    <div>
        <input type="radio" ng-model="color" value="red" /> Red<br/>
        <input type="radio" ng-model="color" value="green" /> Green<br/>
        <input type="radio" ng-model="color" value="blue" /> Blue<br/>
        
        <div ng-switch="color">
            <div ng-switch-when="red" class="box red"></div>
            <div ng-switch-when="green" class="box green"></div>
            <div ng-switch-when="blue" class="box blue"></div>
            <div ng-switch-default class="box black"></div>
        </div>
    </div>
</div>

.box {
    width: 100px;
    height: 100px;
}
.red {
    background-color: red;
}
.green {
    background-color: green;
}
.blue {
    background-color: blue;
}
.black {
    background-color: black;
}