Untitled

<!DOCTYPE html>
<html>
<head>
    <style>
        div {
        display: inline-block;
        width: 150px;
        padding: 2px;
        margin: 5px;
        }
    </style>
</head>
<body>
<?php

for ($red = 0; $red <= 255; $red += 51) {
    for ($green = 0; $green <= 255; $green += 51){
        for ($blue = 0; $blue <= 255; $blue += 51){
            echo "<div style='background-color: rgb($red, $green, $blue)'>rgb ($red, $green, $blue)</div>";
        }
    }
}
?>

</body>
</html>