The Display column shows the graph display settings for the signal. The column contains two boxes; the visible box and the color box.
The visible box is a check box such that when checked, the signal's graph is visible in the graph area, otherwise it is invisible. It has effect only in joint view. Clicking the check box switches between checked (visible) and unchecked (invisible). At most three graphs can be visible at a time. If you check the visible box of a fourth signal, another signal's visible box will be unchecked, and its graph will accordingly disappear.
The color box shows the color of the graph of the signal. Clicking the color box opens a color picker dialog, where you can choose another color for the graph. Clicking OK in the color picker dialog applies the new color to the graph.