The cairns at Balnuaran of Clava show a structural relationship to the annual cycle, most clearly in their alignment on Midwinter sunset. The stones used in their construction fall into simple colour classes: ‘red’, ‘white’ and ‘black’. All three, but especially the black, appear to show selective arrangement in the cairns. A preliminary study of the relationships between the position of coloured stones and certain solar alignments, using both direct opposition and shadow casting, indicates that choice of colour may have been a significant factor in the positioning of stones within the monuments. Moreover the three colours seem to show a consistent pattern of meaning across a wide spectrum of cultures, which may imply a universal psychological factor in their symbolic use.