Large linear gradients, also referred to as split-fountain or iris printing. See also the tags for gradients and rainbows
Contributed by Florian Hardwig
Contributed by Rob Hudson
Contributed by 205TF
Contributed by Stiftung Buchkunst
Contributed by Benoît Bodhuin
Contributed by Maria Doreuli
Contributed by Swiss Typefaces
Contributed by Nick Adam
Contributed by Dingpress
Contributed by Two Points