Billion/milliard dichotomy, the yellow ones using myriads
My guess
correct, yes
darker red indicates places that use milliard to mean 10⁹ and trillion to mean 10¹²
brighter red indicates places that use billion to mean 10⁹ and trillion to mean 10¹²
blue indicates places that use milliard to mean 10⁹ and billion to mean 10¹²
purple indicates places that use both milliard and billion to mean 10⁹ and both billion and trillion to mean 10¹²
yellow indicates places that name their numbers something else entirely