color.4th —
    FreeBSD color-detection boot module
The file that goes by the name of
    color.4th is a set of commands designed to simplify
    color logic. The commands of color.4th by themselves
    are not enough for most uses. Please refer to the examples below for the
    most common situations, and to
    loader(8)
    for additional commands.
Before using any of the commands provided in
    color.4th, it must be included through the
  command:
include color.4th
This line is present in /boot/loader.4th
    file, so it is not needed (and should not be re-issued) in a normal
  setup.
The commands provided by it are:
  loader_color? 
  - Returns FALSE if the 
loader_color environment
      variable is set to “NO” (case-insensitive) or
      “0”. Otherwise returns TRUE (unless booting serial). 
 
The environment variables that effect its behavior are:
  - loader_color
 
  - If set to “NO” (case-insensitive) or “0”,
      causes 
loader_color? to return FALSE, indicating
      to many modules that color should not be used. 
 
  - /boot/loader
 
  - The
      loader(8).
 
  - /boot/color.4th
 
  color.4th itself. 
  - /boot/loader.rc
 
  - loader(8)
      bootstrapping script.
 
Standard i386 /boot/loader.rc:
Use color where applicable:
The color.4th set of commands first
    appeared in FreeBSD 9.0.
The color.4th set of commands was written
    by Devin Teske
  ⟨dteske@FreeBSD.org⟩.