The original blue has been dubbed by most collectors as ‘cobalt blue’ due to it’s deep blue color. Vintage cobalt is a much bluer shade of blue than post-86 blue, which is darker.
Vintage cobalt was produced from 1936-1951, where it was discontinued. HLC brought back the much darker cobalt in the Post86 revival and has not retired it yet.
Sources: DrivingForDeco, VintageAmericanPottery, ShannonZPhotography