.input__colour {
    display: inline-block;
    width: 40px;
    height: 20px;
    overflow: hidden;
    border: 1px solid #222;
    background: #222;
    border-radius: 2px;
    transition: border-color .2s;
    cursor: pointer;
}
.input__colour:hover,
.input__colour:focus,
.input__colour:focus-within {
    border-color: var(--accent-colour);
}
.input__colour__overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 20;
    background-image: radial-gradient(ellipse at center, rgba(255, 255, 255, .2) 0%, rgba(0, 0, 0, .4) 100%);
    background-size: 80px 40px;
}
.input__colour__control {
    border-width: 0;
    position: absolute;
    top: -5px;
    left: -5px;
    width: 100px;
    height: 100px;
    z-index: 10;
}