Rehearsal symbols can be highlighted in red (also colors text.)
The color cannot be customised.
  • Windows
  • Mac

Windows

Settings > Highlight Rehearsal Symbols toggle on/off

Mac

iReal Pro (Mac) v2023.11 or higher
Use the Aa (Chord chart settings) button (top right) to toggle on/off
 
 
 
For older Mac versions v2023.7 or below
Click on iReal Pro/Settings/General to enable Highlight rehearsal symbol.