This is a new-ish Pango feature.
Colorful <span underline="low" underline-color="blue"><span underline="double" underline-color="red">under</span>lines</span> and <span background="pink"><span underline="error">mo</span><span underline="error" underline-color="green">re</span></span>
-Colorful <span strikethrough="true" strikethrough-color="magenta">strikethroughs</span>
+Colorful <span strikethrough="true" strikethrough-color="magenta">strikethroughs</span> and <span overline="single" overline_color="green">overlines</span>
Superscripts and subscripts: 𝜀<span rise="-6000" size="x-small" font_desc="italic">0</span> = 𝜔<span rise="8000" size="smaller">𝜔<span rise="14000" size="smaller">𝜔<span rise="20000">.<span rise="23000">.<span rise="26000">.</span></span></span></span></span>