JARS v52n3 - Results of a Comparison of the Three Editions of the RHS Colour Chart

Results of a Comparison of the Three Editions of the RHS Colour Chart
Donald H. Voss
Vienna, Virginia

The following extract from HortScience 33(1):13-17 is presented by permission of the American Society for Horticultural Science

The Royal Horticultural Society Colour Chart is widely used as a standard in horticultural color evaluation. A colorimetric comparison of the 1955, 1986, and 1995 editions shows significant differences among some of the corresponding color patches. Concentrated in Fan 2 (the "purple" fan), these threaten communication when color identification based on one edition is later referred to a different edition.
The three editions may be identified by their packaging: 1966 in a cardboard box with removable top, dark grayish greenish-blue label; 1986, plastic flip-top box, silver-gray; 1995, plastic flip-top box, dark green. The 1986 edition is marked "Flower Council of Holland" in addition to "Royal Horticultural Society." Each color patch in the 1986 and 1995 editions has a 15/32-inch hole in the center.
To minimize the chances for mis-communication of color data when using the RHS Colour Chart, the following steps are recommended:
The edition of the chart should be indicated in a description; e.g., "RHS66 72 A" for patch 72 A of the 1966 edition. In visualizing color from such a reference, one should refer to the edition specified, especially for the purplish red, purple, and blue colors in Fan 2.
For critical applications, such as cultivar epithet registrations, plant patents, and scientific research, reference to the 11 screen-printed leaves (especially the C and D letdowns) should be avoided; citation of bracketing lacquer patches with appropriate modifiers ("slightly redder [bluer] than," etc.) should yield more reliable color references. (The screen-printed leaves are numbered 57, 66, 74, 78, 80, 81, 82, 87, 88, 89, and 109.)
Because plant colors frequently fall between patches in any color chart, referring to a range between two patches is often desirable.