Preview App bug - "Highlight" shortcut not working normally I'm not able to use "Highlight" shortcut. No matter I press control+command+h or control+command+u, it results in underlining text. Clicking the "Highlight" button also underlines text. I can highlight text using highlight with specific though. 

But it's quite inconvenient that I am not able to use shortcut to highlight. How could I fix it?
Try clicking the highlight button (while not having any text highlighted) and select the highlight colour. It'll show a check mark beside the one you choose. Then unclick it and try the highlight shortcut again and it should make the default that colour highlight.