The orange ones are empty chamber flags.
If that piece of plastic is in the chamber, then a cartridge isn't in the chamber.
It also keeps the action open a bit, for those actions that can't be locked open.
The 'flag' end can be seen from a long way off.

"A Chamber Flag shows a SAFE Weapon. Also known as Open Bolt Indicator (OBI) or Empty Chamber Indicator (ECI), the brightly colored flag alerts the range officer and other shooters that the fire arm chamber is empty."