What more can be said that hasn't already. THE Modernist furniture design icon of the C20th ( more so than Le Corb's chaise ). Simply awe-inspiring. This really is purely a piece of sculpture to admire. POA.
The 2 photos above highlight the decisive step Rietveld took, c.1918, to incorporate De Stijl ideas and colours into his work. The wood version, whilst still a striking shape, does not have the impact of the painted version. Interestingly, Rietveld pared the original version down even more, by removing the side panels under the armrests. Even though Rietveld never met Mondrian he soaked up his & Van Doesburg's influence when colouring the chair.
Shown above is a plan of all the components for the chair. Rietveld at the time was searching for ways to mass produce chairs, and the chairs give the impression of having been mass produced. However, their unusual design and the finishing make them difficult to produce in volume; the best you can make them in is small batch production. The chairs produced by Rietveld & Van Groenekan were made in several sizes, there was no standard size as such.
This chair design was so visually strong that there have been many variations over the years, including by Rietveld himself. Some of these are shown of the 'Red Blue chair variations' page.