I am not at all an admirer of the work of Hector Rojas in his book "Origami Animals". but it is not the fact of colouring a model that makes it in some way unworthy. No amount of colouring can improve a model that is already inferior or downright bad before the colouring is applied. But that is something very different from saying that the application of colour necessarily detracts from its merits. Colouring is a matter of individual taste and coloured origami may be good or it may be bad. Just as I admire unpainted terra cotta pots, so I, myself prefer my origami unpainted, but this is only my personal taste.
We greatly admire the architecture and sculpture of Gothic Europe and almost universally visualise it in its present state as unpainted stone or wood. Yet this is not how the people of the middle ages saw their buildings. The whole of the interior of Gothic buildings were often colourfully painted in what to us would seem bizarre and lurid designs. Sculpture, in wood and stone was also frequently brightly and colourfully painted. Only a few scraps of painted buildings remain and most mediaeval sculpture has lost its colouring., but the tradition of colouring sculpture continued into the Baroque era. Indeed, there is still a tradition for painting inferior, sentimental statuettes of saints today. Usually the statues before being painted are pretty poor and painting does nothing at all to improve them.
In a few instances small parts of the stonework interiors of ancient churches have been repainted to give a suggestion of what the buildings looked originally looked like. Sculpture, especially of tombs and armorial bearings has more often been fully repainted, though not without opposition from some objectors.. However, to experience something of the appearance of a fully painted mediaeval interior we must look at some of the Victorian Golhic revival churches, which, while built in a different spirit, do give an a idea of how the mediaeval buildings which we so admire, originally looked.
Today, we admire Gothic architecture not for its colour, but for its form and there has been no rush to repaint the great churches.We fear that colour would detract from their perfection of form. But we must recognise that the original builders would certainly not have agreed!