show.css

*:not(b):not(i):not(body) {
    border-width: 5px;
    border-style: solid;
}

body {border: none;}
body>* {border-color: rgb(255,   0,   0);}
body>*>* {border-color: rgb(255, 255,   0);}
body>*>*>* {border-color: rgb(  0, 255,   0);}
body>*>*>*>* {border-color: rgb(  0, 255, 255);}
body>*>*>*>*>* {border-color: rgb(  0,   0, 255);}
body>*>*>*>*>*>* {border-color: rgb(255,   0, 255);}