Change background color based on variable with PHP

To change a webpage or html background based on what a PHP variable is, follow this guide:

For practical purposes if a profile is online the PHP variable = 1 making the background green otherwise make it red for 0.

functions.php

function is_online($id){
    $data = json_decode(file_get_contents("https://someurl/profile?userid=" . $id . ""));
    $status = $data->response->status;
if($status == 1){$color = 'green';}else{$color = 'red';}
return $color;
}

More html here