JQuery problem? Themes don't change

Hello, I am not able to change the datepicker themes, I always see a light/dark grey version with very dark date numbers that are hard to read. The cursor is always blue. That can i do to avtivate other themes or to dispable theme function completely (also does not work at the moment)

Thank ou for quick reply

https://www.ads-software.com/extend/plugins/contact-form-7-datepicker/