.btn-primary, .btn-primary:hover, .btn-primary:active, .btn-primary:visited {
background-color: #8064A2 !important;
}
<div class="btn-group btn-group-toggle" data-toggle="buttons">
<label class="btn btn-secondary active">
<input type="radio" name="options" id="option1" autocomplete="off" checked> Active
</label>
<label class="btn btn-secondary">
<input type="radio" name="options" id="option2" autocomplete="off"> Radio
</label>
<label class="btn btn-secondary">
<input type="radio" name="options" id="option3" autocomplete="off"> Radio
</label>
</div>