As your reference is, unfortunately, in Greek, I cannot refer to the actual quotation. However, I suspect that Ruskin was writing about drawing and painting, not architecture and that he was using the example of architectural mouldings being picked out in a contrasting colour to that of the walls or ceilings as a waspish criticism. In other words, if you use colour in your work to try to show form, you should give up fine art and become a housepainter instead.

--------------------------------------------------
Note added at 2 hrs (2011-08-24 19:20:46 GMT)
--------------------------------------------------

I equally suspect that Ruskin was not writing specifically about drawings/paintings of buildings, but about drawing and painting in general. The Impressionists later used light and colour in a way that dissolved form.

--------------------------------------------------
Note added at 16 hrs (2011-08-25 08:29:01 GMT)
--------------------------------------------------

Thanks for the reference, I had forgotten how good Ruskin was and must get a paper copy! The reason Ruskin used the example of architectural mouldings was simply that, given the Victorian fashion for applying them to their walls and ceilings and picking them out using colour, it was a very familiar image. The mouldings broke the flatness of the surfaces they were applied to and picking them out in colour was meant to both draw attention to them (it showed you had the money to buy them and some were much more expensive and exclusive than others) and to emphasise their effect. He also uses apples and cheeks as images to make the same point.

By superimposed colour, I don't think he means layering washes of colour, but superimposing local colour on the object. I take back what I wrote above about Ruskin dismissing atmospheric perspective, as he convincingly defends it here. However, I still think he is quite wrong about hue and advancing and recessive colour, though to a large extent he is arguing in opposition to the mechanical understanding of that effect. The apparent distance effect of a colour does depend on how it relates to other colours around it. Some years ago, I painted the ceiling of a small, high-ceilinged room in a dusty mid-tone pink to lower it and make the room seem larger. I believe it worked very well and other people agreed. Had I painted the walls red, it would not have worked, but painting them pale grey allowed the pink to have the effect of advancing the surface it was painted on.