The red colouration observed in many sand seas is a consequence of fine grained haematite and clay coatings surrounding quartz grains and a number of hypotheses have been proposed to account for this. The marked increase in dune redness with increasing distance inland in the northern area of the Namib sand sea is investigated using satellite imagery and mineral magnetic measurements. These results suggest that source materials exert at least a partial control on dune colour in this field setting, but that evidence for the influence of other factors (e.g. climatic gradient and/or abrasion of coating during transport) is also present.