To get started, be sure to login in or register first. Then, right under the navigation bar, locate where it says "Welcome, " and your username. Click the link that is your username to bring you to your profile editor.
On the profile editor screen, locate the Plot Colors option. Underneath it, select a color scheme using the dropdown menu or choose to remain with the default. If you scroll down the page further, you can see a graph of all available color schemes. Once you've selected a scheme, press the Update button to save your selection. Then browse the site to see the changes take effect!