Colour Classes
The class limits shown below (Fig. 3) have been chosen after examination of the Munsell Soil Color Charts (Munsell Color 2010) and the scheme used for grouping in the Factual Key (Northcote 1979). A major aim was to achieve class limits as simple as possible and to standardise on these throughout the system. The proposed scheme has the virtue of simplicity although some may argue that 2.5YR 4/2 for example is not very grey, nor is 5YR 8/3 very red. These discrepancies can of course be removed, but at the cost of simplicity. Some of the more obvious 'misfits' are probably rare in soils. Colours should be matched to the chip closest in colour, or the nearest whole number in chroma where chips are not provided, for example chromas 5 and 7.
Figure 3. Colour class limits. DO NOT use this in lieu of Munsell Soil Color Charts in the field.
* In some regions, especially south-western Western Australia, common usage is for the colour yellow to be asigned for hues yellower than 5YR, value 5 and chroma 3 or greater. This is an acceptable variation in the ASC.
| Black | The dominant colour (moist) for all hues has a value of 3 or less and a chroma of 2 or less. |
| Red | The dominant colour (moist) has a hue of 5YR or redder and a chroma of 3 or more. |
| Brown | The dominant colour (moist) has a hue yellower than 5YR and a value of 5 or less and a chroma of 3 or more. |
| Yellow | The dominant colour (moist) has a hue yellower than 5YR and a value of 6 or more and a chroma of 4 or more. |
| Grey | The dominant colour (moist) for all hues has a value of 4 or more and chroma 2 or less; for hues yellower than 5YR values of 6 or more and chromas of 3 are allowed. |
Gley colours
Greyish, greenish and bluish colours found in wet soils and defined by specific Munsell Soil Color Charts - usually 10Y - 5GY and Gley charts 1 & 2 (Munsell Color 2010).