galaxy/config/plugins/visualizations/PCA_3Dplot/static/style.css

#visualisation {
    width: 100%;
    height: 92vh;
}

#combos {
    width: 100%;
}

select {
    /* styling */
    background-color: white;
    border: thin solid black;
    border-radius: 4px;
    display: inline-block;
    font: inherit;
    line-height: 1.5em;
    padding: 0.5em 3.5em 0.5em 1em;

    /* reset */

    margin: 0;      
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    -webkit-appearance: none;
    -moz-appearance: none;
}

select.minimal {
    background-image:
    linear-gradient(45deg, transparent 50%, gray 50%),
    linear-gradient(135deg, gray 50%, transparent 50%),
    linear-gradient(to right, #ccc, #ccc);
    background-position:
    calc(100% - 20px) calc(1em + 2px),
    calc(100% - 15px) calc(1em + 2px),
    calc(100% - 2.5em) 0.5em;
    background-size:
    5px 5px,
    5px 5px,
    1px 1.5em;
    background-repeat: no-repeat;
}

select.minimal:focus {
    background-image:
    linear-gradient(45deg, green 50%, transparent 50%),
    linear-gradient(135deg, transparent 50%, green 50%),
    linear-gradient(to right, #ccc, #ccc);
    background-position:
    calc(100% - 15px) 1em,
    calc(100% - 20px) 1em,
    calc(100% - 2.5em) 0.5em;
    background-size:
    5px 5px,
    5px 5px,
    1px 1.5em;
    background-repeat: no-repeat;
    border-color: green;
    outline: 0;
}

label {
    color: #000;
    font-weight: bold;
    display: inline-block;
    width: 200px;
    text-align: center;
}