low_search custom field searchf

    {exp:low_search:form required="keywords" collection="my_collection" query="{segment_x}" result_page="search/results"}
        <input type="text" name="keywords">
        <input type="text" name="search:custom_field:colx">
        <select name="category[]">
            <option value="">Everywhere</option>
            {exp:channel:categories category_group="1" style="linear"}
            <option value="{category_id}"{if low_search_category ~ '/\b'.category_id.'\b/'} selected{/if}>
                {category_name}
            </option>
            {/exp:channel:categories}
        </select>
        <button type="submit" class="btn btn-primary mb-2">Search</button>
    {/exp:low_search:form}