Tahoe wildflowers. I saw many clumps of this plant on my hike round the Meiss Meadows back in July. I'm not sure what it is- the flora of North America is very different to the UK but then again it's often possible to discern similarities.
 The nodding bell shaped flowers put me in mind of some of the Comfreys (i.e. Symphytum species) though the foliage looks different. This makes me think it might be of the Boraginaceae family. Pulmonarias are also of the Borage family and also have nodding bell flowers which in some cases morph from blue to pink to mauve e.g. the Common Lungwort (P. officinalis).
 A number of plants whose flowers undergo this transformation are graced with the common name of Abraham, Isaac and Jacob- presumed to be a reference to the changing colours. In fact all the ones I can think of are fellow Borages. Perhaps the plant I saw in great profusion on the Tahoe trails is an American cousin?