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.