Edit in JSFiddle

<div ng-app ng-init="r=128; g=128; b=128;">
    <div class="block" style="background-color: rgb({{r}}, {{g}}, {{b}});"></div>
    <input type="range" min="0" max="255" step="1" ng-model="r">
    <input type="range" min="0" max="255" step="1" ng-model="g">
    <input type="range" min="0" max="255" step="1" ng-model="b">
    <p>Drag the sliders</p>
</div>

.block {
    width: 100%;
    height: 150px;
}

input {
    display: inline-block;
    width: 30%;
}