Edit background recaptcha

Hello,

How can you change the color of the recaptcha background?
I’ve tried adding the following to custom CSS

.rc-anchor-dark {
    background: rgba(30,46,64,0.7);
    border: 1px solid #525252;
    color: #fff
}

but I’ve get the following error (after saving):

ut in anonymous-file-0.less on line 1, column 1037 1| @primary_color : #37e89b;@bg_image : ‘http://www.mindofmedia.eu/achtergrond_login.jpg’;@bg_image_repeat : no-repeat;@bg_image_size_type : cover;@bg_color : undefined;@font_family : Raleway;@font_variations : undefined;@font_subset : undefined;@font_size : 20;@font_color : #ffffff;@redirect_login : undefined;@redirect_register : undefined;@template : mercury;@logo_hide : 1;@logo_image : undefined;@logo_bg_size_type : cover;@logo_width : 100;@logo_height : 100;@logo_link : undefined;@logo_title : undefined;@form_placement : left;@form_heading : undefined;@form_bg_image : undefined;@form_bg_size_type : cover;@form_bg_image_repeat : no-repeat;@form_bg_color : rgba(30,46,64,0.7);@form_padding : 40px 40px 40px 40px;@form_no_shake : undefined;@form_animation_in : undefined;@form_animation_out : undefined;@form_animation_error : undefined;@form_button_color : #ffffff;@form_button_bg_color : #1e2e40;@form_captcha : 1;@form_captcha_key : 6LdidA8TAAAAABIWW1KumyrWoj1cw6knuGtHa0gt;@form_captcha_theme : dark;@form_captcha_type : audio;@custom_css : .rc-anchor-dark { 2| background: rgba(30,46,64,0.7); 3| border: 1px solid #525252; 4| color: #fff 5| };@custom_js : undefined;

The website is at beautyminded.be

https://ww.wp.xz.cn/plugins/tesla-login-customizer/