We can create other panels in addition to the main panel with a call to

        GLUI_PANEL

Since we want our new panel inside the main panel, we pass the pointer mainPanel as the first parameter to the constructor. The second and third parameters set the style of the panel. We add a label to our new panel with the string "Set Base Color". For this text to appear, we must choose either GLUI_PANEL_RAISED or GLUI_PANEL_EMBOSSED as the third parameter; we use the latter for our example.