So the IAS is your indicated air speed. The TAS is your true air speed. Your PFD shows the IAS.
Overspeed is indicated by going into the red band.
Your maximum speed depends on multiple factors. Your altitude, your flaps setting etc.
Your maximum speeds are often written down on a label inside the cockpit. I am not quite sure, if the 787 has one. On this label you will find operation speeda for normal flight, with landing gear, flaps etc.
Thanks for the infos but I’m talking which speeds are relevant damaging? The cruise speed maximum on wiki is indicated as 0.89 MACH. Right now I’m at .891 MACH. The IAS is still not in the red though. That’s why Im wondering which one is implemented as damaging the airplane? Only IAS? Or also TAS?