The Munsell Palette for December 2012 looks at fir trees.
Figure 1: Munsell colors for December 2012
This month, while some of us wait for snow, we look at fir trees, emblematic of various winter holidays. The particular tree we're looking this time is a Blue Spruce, native to Colorado and cultivated widely for Christmas tree use. We will see that despite its name, it is actually a long way from blue!
For the most part, when you are looking at a fir tree, you are looking at its needles, which we will focus on here. The needles have two distinct colors; the topside that faces the sky and sun, and the underside (seen from below) that faces the ground. Looking closely, there is also a yellowish color along the edges that can be seen in direct sunlight.
Needle topsides (2.5GY 4/4)
The average local color of the topsides of mature needles is 2.5GY 4/4. As with all colors, they drop in value as they fall into shadow, but this represents an average under direct or indirect daylight. The surface of the needles is reflective and can dramatically rise in value in direct light, but the hue holds steady.
Needle undersides (10GY 5/2 & 10GY 6/1)
The underside of the needles of the Blue Spruce are still in the green-yellow range of the spectrum. They are 3/4 of a Munsell hue division in the direction of blue, however, and so by comparison, they are bluer in hue than the topsides of the needles. Color perception is based strongly in comparison and adaptation: an object doesn't have to be blue to appear blue to us; it just has to be bluer than what's around it (or, technically, reflect more blue wavelengths of light into our eyes). The undersides are lighter in value by a full one to two steps, and significantly lower in chroma.
The needles in this sample are about 10GY 5/2.
And in an area of more direct light, we're at about 10GY 6/1. Sharp-eyed observers of this image will see that the chip is actually a bit more chromatic than the needles, even at chroma 2. The book of samples does not have a chroma 1 chip for 10GY at value 6, but we can see from observation that it's lower. Since chroma 0 is a neutral gray, we can approximate this hue at around chroma 1. If we use chroma 2 in our 10GY 5/2 sample above, we need to make sure we come down in chroma slightly for more washed-out areas; it would be too chromatic to use 10GY 6/2, a full value step higher at the same chroma.
Needle tips (7.5Y 6/6)
If observing a Blue Spuce in direct sunlight, a close examination will show sunlit edges where the needles are physically thinner, and subsurface scattering reflects more yellow sunlight. If you're painting a full tree at a distance, this is unlikely to be perceived, but in close-ups it can be a nice touch when applied with subltety. Predictably, the yellow sunlight pulls strongly towards the yellow part of the spectrum, with a significant increase in chroma to 7.5Y 6/6:
In overcast or indirect light, this effect will be much less noticeable, and may even disappear completely.
Now, obviously, if a Blue Spruce is moved indoors and covered with colored lights, it will appear dramatically different (and festive). And a mountainside of fir trees painted at a distance is not going to show much of the variation we see here, but be basically the averages of all of these colors filtered through atmospheric perspective, rendered through light and shadow values. However, a careful rendering of an outdoor tree can be executed with the basic colors listed in this article.