A bench comprising Chief Justice H L Dattu and justices A K Sikri and R K Agrawal modified a 2013 order and granted permission to use red beacons in such vehicles by authorities.
The city government's plea averred that according to the Rayleigh theory in physics, red light has the maximum wavelength, resulting in maximum penetration even through low visibility conditions.
It further said many countries like the USA, Australia and Canada used red colour beacon light for emergency vehicles and it should be allowed here too.
The Delhi government's plea that red is the "best" colour for vehicles was not opposed by senior advocate Harish Salve, appearing as an amicus curiae in the PIL on the issue.
The court has now posted the PIL for final hearing in April and asked the states to file their responses within two weeks.
In December 2013, the apex court had held that red beacon be allowed to be used only by persons holding constitutional posts and high dignitaries to prevent its misuse.
The court's order was passed on a PIL filed by Uttar Pradesh resident Abhay Singh on misuse of red beacon.
It had said the red light has become a status symbol and that police personnel, who are put on duty for giving security cover to VIPs, should be deployed for better purposes like making the roads safe for women.
