Q. Assertion: Danger signals are made of red colour.
Reason: Velocity of red light is maximum and thus more visibility in dark.

 8188  215 AIIMSAIIMS 2000Ray Optics and Optical Instruments Report Error

Solution:

Red colour is always used for danger signals, because as red colour is having the longest wavelength, it is the least scattered. So, this signal can be seen from a very long distance.