Occurrences in the Bible
The English word "yellow" appears only four times in the King James Bible translation. It is derived three times from the Hebrew word tsahob (Strong's Concordance #H6669) and once from the word yeraqraq (#H3422).
Background
Yellow has an HTML hex code of #FFFF00. It is a color, on the visible spectrum, with a wavelength between 570 to 580 nanometers. It sits, on a conventional color wheel, between orange and green.
A primary color is one that can be mixed, in varying amounts, to produce a plethora of other colors depending on the application. Red, yellow and blue (RYB) are considered traditional primary colors in dyes, pigments, and paints. They can be mixed to make secondary colors such as orange, green, and purple. Red and green can be mixed, in equal parts, to produce yellow.
For printing, cyan, magenta, and yellow (CMY) are considered primary colors. When they are combined they produce black.
Yellow can be derived from a variety of sources. Yellow ochre, a clay earth pigment, and orpiment, a mineral containing arsenic sulfide, have been used to retrieve the color. Lead tin oxide can produce it as well. Dyes can additionally be extracted from weld leaves and oak bark.
Biblical Symbolism
Yellow can represent prosperity. King David, in Psalm 68, rejoices over Israel's successful occupation of the land of Canaan. He uses the Hebrew word yeraqraq for yellow to describe how glorious ancient Israel was when it entered the Promised Land.
"Kings of armies flee, they flee, And she who remains at home divides the spoil.
"Though you lie down among the sheepfolds, You will be like the wings of a dove covered with silver, And her feathers with yellow (yeraqraq) gold." (Psalm 68:12 - 13, NKJV).
Yellow can also symbolize disease. The color appears three times in Leviticus 13, a chapter that discusses the diagnosing and treatment of skin disorders among the Israelites. Verses 30 and 32 deal with leprosy, either on a person's head or beard, where the hair turns yellow.
If a man or woman have a plague upon the head or the beard; then the priest shall see the plague: and, behold, if it be in sight deeper than the skin; and there be in it a yellow (tsahob) thin hair; then the priest shall pronounce him unclean: it is a dry scall, even a leprosy upon the head or beard.
And if the priest look on the plague of the scall, and, behold, it be not in sight deeper than the skin, and that there is no black hair in it; then the priest shall shut up him that hath the plague of the scall seven days:
And in the seventh day the priest shall look on the plague: and, behold, if the scall spread not, and there be in it no yellow (tsahob) hair, and the scall be not in sight deeper than the skin;
He shall be shaven, but the scall shall he not shave; and the priest shall shut up him that hath the scall seven days more . . . (Leviticus 13:29 - 32, KJV).
Leprosy rendered a person ceremonially unclean until it went away.
A Prophetic Color
Revelation 9 discusses the first two of three woes that will come upon mankind during the end time Great Tribulation. The first woe (verses 1 to 11) entails humanity tormented for five months (verse 5).
The second woe (Revelation 9:13 - 21) is the unleashing of a huge army that will ultimately kill a third of all humans. This army wears breastplates or armor that look like fire (red or scarlet), jacinth (blue), and brimstone (verse 17).
And so I saw the horses in the vision, and those sitting on them, who had fiery breastplates, even like jacinth and brimstone. And the heads of the horses were like heads of lions, and fire and smoke and brimstone shoot out of their mouths. (Revelation 9:17, HBFV).
The meaning of the Greek word translated "brimstone" (Strong's #G2306) in Revelation 9:17 above is "sulfur" or "sulfurous." Brimstone is a stone that can be set on fire and which gives off a yellow color due to its sulfur content.
Brimstone is also used in other parts of Scripture, most notably as one of the two substances (the other being fire) that rained down from heaven to destroy Sodom and Gomorrah. Lot's wife saw, before turning into a pillar of salt, witnessed a downpour of these two destructive forces on the cities and the surrounding region.
Then the Lord rained upon Sodom and upon Gomorrah brimstone and fire from the Lord out of heaven (Genesis 19:24, KJV).
More Info on Yellow
In the 1890s, pencil makers in the United States began coloring their writing implements yellow due to its association with Chinese royalty (China had the best graphite at the time). Today, American pencils retain this tradition.
Yellow is commonly used throughout the world. Traffic lights and signs use it to symbolize caution when traveling. In most cultures, it also represents sunshine, happiness, and warmth. In religions such as Hinduism and ancient Egyptian, yellow is often associated with their deities.
Recent research reveals that black type against a colored yellow background is the best combination for printed material. Tests also show this print combination is the best concerning readability and in the ability of our minds to retain information.
Yellow is the most visible light of the spectrum, its high reflectance allows it to act as a secondary light source. It is the first wavelength of light processed by the human eye (which belies its use in certain signage and on some emergency rescue vehicles).
Our peripheral vision (the ability to see side or fringe areas when we look straight ahead) is 2 1/2 times higher for the color yellow than for red.
Frankincense is one of several gifts brought by the Parthian Magi when they came to worship Jesus Christ sometime after his birth. Frankincense, which is yellowish in color, is a dry, rather odorous resin that although grown in Palestine was also imported from Arabia (Jeremiah 6:20, Isaiah 60:6).
The Bible says the New Jerusalem created by God will have twelve foundations, with each one shining a different kind of light based on a particular precious stone (Revelation 21:19). The seventh foundation (seven is the number of perfection) has Chrysolite within it. The Greek word translated "chrysolite" is a gem that looks like gold or yellow.