So, imagine the Slide Design task pane is open, and you scout around in it to find and apply a template. After you've applied the template to all your slides, you decide to put a different color scheme on the title (first) slide.
This task pane helps the process by giving you a link, Color Schemes, near the top. The link instantly shows thumbnails of the color schemes in the task pane. You could also open color schemes from the Other Task Panes menu—but it's a slightly longer way.
CTRL+F1 closes the task pane or opens it; this works in all Office programs.
ALT+S opens the Slide Design task pane, but only if the Slide Design button is displayed on the Formatting toolbar.