How do I change the color/width of an existing line in Acrobat Pro?

If I open a pdf and choose "Edit PDF", I can select existing lines and use the mouse handles to resize them, but there aren't any color or line width icons on the toolbar.

If I open a pdf and choose "Comment", the drawing toolbar appears (with text, various shapes, and fill and width icons), but I can't select the existing lines. The mouse cursor doesn't change appearanche when I hover over a line. Right-clicking on existing lines displays the Document shortcut menu rather than the line shortcut menu.

When in Comment mode, I can draw new lines and change their colors, but I can't change the color of existing lines.