It's a richer visualization than that. The Sieve of Eratosthenes only marks which numbers are composite -- this visualization actually shows each of the factors.
Re:Prime Number Patterns
by stillbourne on Tuesday July 07, 2015 @11:39PM
(#9849683)
This is merely a prettier but somewhat obfuscated Sieve of Eratosthenes: https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes