Answer:
1. The home tab
2. Font group
3. The small arrow at the bottom right of the font command group.
4. On "Font" heading (then "All text" subheading)
Explanation:
The following explanation will help Su in accomplishing her task.
1. Go to the home tab;
2. From the home tab, Su will have access to various command groups but in her case, she needs the Font command group.
3. There's a small arrow located at the bottom left of the font command group section; clicking on this arrow will open the font dialogue.
4. On the font dialogue, there are two headings. The "font" heading and the "character spacing" heading.
In her case, she needs the "Font" heading. The font heading also has various subheadings. To access the underline colour option, she needs the "All text" subheading.
See attachment for picture guide.