Pure colours

There's a prism hanging in my window that faces east. It's part of an old chandelier. This morning the colours dancing on the wall were moving around a lot and broken into folds. I'd never seen it like that before. Wasn't sure why. The only reason I could think of was that the sun had moved south and was shining at an angle through the branches of a big ash tree which is losing its leaves. These colours haven't been saturated, and the dark background was how the camera recorded it, because of the contrast with the bright light. The wall is really a pale cream.