Among Us' developer Innersloth has revealed that it landed in hot water for violating the Geneva Convention with the game's med bay on the Skeld map.
In the original design of the med bay, red crosses can be seen on either side of the doors. This violated the Geneva Convention, and so the design had to be changed to feature blue crosses instead.
Misuse of the Red Cross is taken very seriously, as it is seen to distort its meaning and protective value. That explains why a lot of games opt for a red medkit with a white cross on it, then.
Considering the amount of murders committed in Among Us' med bay, it was probably for the best the game decided not to use the widely recognised symbol of the Red Cross.