funky-framadate-front/src/assets/scss/themes/_dark.scss

#big_container {
    &.theme-dark-crystal {
        background: #222;
        color: #ddd;

        main {
            background: #444;
        }

        h1::after {
            background-color: #1b6d85;
        }

        .btn--primary:focus,
        .btn--primary:hover,
        .btn--primary:active,
        .btn--primary {
            background-color: #1b6d85;
        }

        .btn--warning:focus,
        .btn--warning:hover,
        .btn--warning:active,
        .btn--warning {
            background-color: #554685;
        }

        select {
            background: #1b6d85;
            border-color: #1b6d85;

            &:hover {
                color: #ccc;
            }
        }

        .title {
            color: #ccc;
        }

        .lang_icon,
        .menu_icon {
            fill: #1b6d85 !important;
            color: #1b6d85 !important;
        }
    }
}