wiki-grav/themes/learn2-dark/scss/theme/_tntsearch.scss

.tntsearch-form .form-input {
    border: 2px solid lighten($header-bg, 10%);
    background: darken($header-bg, 10%);
    border-radius: 4px;

    label {
        color: rgba(200, 200, 200, 0.8);
    }

    input {
        color: $white;
    }
}

// !important required for some elements to override included CSS
.tntsearch-dropdown ~ .tntsearch-results .row {
    width: auto !important;
    background: #724879 !important;
    padding: 5px !important;
    text-align: left;
    color: #dddddd;
}