When is brown not brown?
Our main tool, however, the Munsell Soil Color Chart, based off of the work of Albert Henry Munsell. In a nutshell, the Munsell Chart tries to put some uniformity into soil colors, because we don't see things the same way. So, when you say "brown", you are assigning a number to it. Actual "brown" in the Munsell Color Chart is 10 YR 4/4. You might think something is brown, then when you hold the dirt to the chart, it's actually 10 YR 4/1, which is a greyish brown (I don't remember them all). As soils get more red, you try a different page in the book (like, say 5 YR or even 5 R). Not too difficult.
Of course, there's still a bunch of subjectivity. Sometimes, a dirt can be sort of in between 2, or even 4 different color numbers. Dirt will change colors as it dries out, and the ambient light can make a difference as well. And then there's mottles...but this is now getting dry. If you have clicked on the links, then you can see that a Munsell "book" as we call it costs a lot of money. I want one, but not at that price. We could have used one today, but we forget to bring one of the office copies, so we relied on the semi-complete 10 YR page that someone let me borrow and tried to make up what the reddish colors we had might be.