If you want to change the color scheme of the WooCommerce Bookings calendar of the customer view, you can do so by modifying a few CSS styles.
If you are not using a child theme for WordPress or your theme does not allow you to enter custom CSS, perhaps you can install the Jetpack plugin which has a Custom CSS Editor built in.
Note: This is a Developer level doc. If you are unfamiliar with code and resolving potential conflicts, select a WooExpert or Developer for assistance. We are unable to provide support for customizations under our Support Policy.
Here are the styles for the different calendar elements: