four-colour

Siegel and Shuster had created a new archetype – or perhaps, more accurately, a new stereotype – and by 1940, once the nascent genre had demonstrated that it could get kids to part with millions of dimes per month, swarms of imitators catapulted hordes of four-colour heroes into the skies, all chasing the gold in this golden age.

When the four-colour theorem was proved in the 1970s, there was plenty of heated discussion among mathematicians, philosophers, and computer scientists.

They are well known, starting with the proof of the four-colour theorem.

A blue alert, called when the sea ice stretches out more than 60 nautical miles, is the lowest tier on China’s four-colour alert system for severe weather, with red being the highest.

A blue alert, called when the sea ice stretches out more than 60 nautical miles, is the lowest tier on China’s four-colour alert system for severe weather, with red being the highest.