Hi David!
Welcome to planDisney! I assume you are referring to the black and blue dots that appear when
purchasing your ticket to the Disneyland Resort online or on the Disneyland App. In order to enter either
Disneyland Park and/or
Disney’s California Adventure Park, a Disney Park Pass reservation is required. When you initiate a purchase online for tickets, you will need to
select the days when you will be visiting the theme parks. A blue dot on the calendar notes that the date is available, the dot turns black when you have selected the date. If you click on the date once it has turned black, it will turn blue, and you can choose another date. Once you are happy with the dates you have selected, you can then proceed to check out.
My recommendation is to make sure you book your
Disney Park Pass reservations early enough to enable you to have the dates that you want. This is especially the case when you are looking to go during the holiday season. Bear in mind that tickets are sold 120 days out, so if your plan is to visit the parks during Christmastime, I suggest you log in to the Disneyland website early and be ready to book as soon as tickets are available.
I hope this helps you plan your magical vacation to the Happiest Place on Earth!
Malanie