The superpanel's appearance is controlled by the built-in themes or the CSS styles. The superpanel themes effects the appearance of all of the superpanel elements such as the tooltip header and tooltip callout.
C1SuperPanel is designed to make customization easy for you. You have endless possibilities in changing its default appearance.
You can apply CSS styles to modify C1SuperPanels elements. C1SuperPanel provides several built-in CSS Selectors that appear when you select the drop down arrow next to the CSSClass property