In this article the only complete copy of the very rare Natural System of Colours by Moses Harris (ca. 1770) is reproduced. The color plates of the two hue circles are compared to those in the second edition of Harris's work (1811) as well as the so-called facsimile edition by Faber Birren of 1963. Comparisons are also made against later reproductions and modifications of these circles, including those by Merimee and Varley. The small number of authentic representations are identified. Four versions of the central triangles of the "prismatic" color circle are compared, including that by the painter J. M. W. Turner. (C) 2004 Wiley Periodicals, Inc.