This is the Tolix A chair, designed by French entrepreneur Xavier Pauchard in 1934.
They are available as chairs, armchairs, benches, stools... in galvanized steel, perforated... in multiple versions.
I have to say I'm not a huge fan of metal chairs; but I do like industrial esthetics. Moreover, I've been seing Tolix chairs all over restaurants and cafés lately and I must admit I'm beginning to like these colorful chairs.
Although, I'd prefer them in grey tones, because I think (in my humble opinion) they're better put as "rough" metal with wood and other neutral colours, such as darker greys, black and white.
More information at Tolix.