Definitely! KnowledgeOS gives you different options to customize the look and feel of your experience. To change themes, among other things, go to your Settings and choose Appearance from the sidebar. You can access Settings through the top button in your Dock and selecting it from the list, as well by opening Navigator (Opt Space on Mac / Ctrl Space on PC) and searching for "Settings".
Below themes you will see options to manage how your dock renders on various pages. To learn about the other Dock settings please read "How do I control where the Dock shows up?"