On this page of the "Colors and line styles" dialog (which can be opened using the corresponding button in the toolbar at the top of the main window), you can set the colors and line styles of the current experimental diffraction data (anchor pattern as well as additional patterns).
For all current experimental diffraction patterns, the current color is displayed in the corresponding box. On the right-hand side of each color box you will find a button "Modify...". By pressing on the button you can open a color selection box where you can select/define a new color for the corresponding graphical element.
It is not only possible to define the color but also the line style and width of the corresponding diffraction pattern. The current line style is displayed to the right of the "Modify..." button; if you press on the small arrow on its right-hand side, you will get a list of available line styles from which you can also select the new line style.
To the right of the line style box, you can enter or adjust the corresponding line width (given in points). Either use the "up" and "down" array buttons to modify the line width, or enter a new value directly.