All over, really. And not to be confused in any way with the newspaper, Stendahl's novel of 19th century France, or Ancient Egypt for that matter. As an aside, the Upper Kingdom of Ancient Egypt was found to the South while the Lower Kingdom was to the North. It was so named with reference to the flow of the Nile River. The "lower" part being where it drains into the Mediterranean Sea to the North. Along the same lines, their "Book of the Dead" actually was meant to show how life should be lived. Life on the other side, that is. Another example of Egyptian counterintuition. No wonder the Israelites had to get out of there. "Neither shalt thou swear by thy head, because thou canst not make one hair white or black." (Matthew 5:36, emphasis mine) In most Bibles, that verse--as it was spoken by Jesus--would be rendered in red.
In the Red
Normally, when someone reads this, they think that whatever business is being referred to is suffering financially. Unable to turn a profit, it looks to lay off employees, tighten the belt and brace for the worst. The "red land" of Ancient Egypt was the barren desert on either side of the arable and fertile banks of the Nile. Seen these ways, the "red" indeed looks to be a negative. Something from which to distance oneself. Blood tends to have that effect, as well. I've never been keen on the concept of vampirism. Always repulsed. Our blood is red because of the iron content. When's the last time (unless you suffer from hemochromatosis--too much iron) that you thought about the trace minerals needed to survive and thrive? Our blood is red because of the oxidation of the iron in the blood, simple as that. Oh, we have white blood cells too, they're just outnumbered seven-hundred to one. I say all of this to say that, while it was against Mosaic law to drink blood (see Leviticus 3:17), condemned, too, by James in the New Testament (see Acts 15:29), imagine what went through the minds of those who were commanded by God to sacrifice an innocent lamb or cow for wrongdoing. When they watched the blood drain from the neck of a helpless animal. The same should be realized in us when we think of Jesus being broken open for our sins, bleeding out on the cross. The sight of blood is revolting. But His blood had to be shed because of sin. And because of our own the only real safe place is to indeed be "in the red".
"But when Jesus heard that, He said unto them, They that are whole need not a physician, but they that are sick. But go ye and learn what that meaneth, I will have mercy, and not sacrifice: for I am not come to call the righteous, but sinners to repentance." (Matthew 9:12-13)
In the Black
While the "red lands" of Egypt may have been barren, useless to plant fields and crops, the Egyptians were able to mine minerals (one of which had to be iron) and precious stones. Conversely, the "black lands" refer to the land nearer the Nile. When the river crested and flooded the banks, the water would provide the conditions necessary to grow crops in order to feed the people. It's no wonder the Egyptians worshipped the river as a god. A similar impulse affected the Syro-Canaanite peoples that the Israelites encountered upon leaving Egypt. Their "Baal" was also a god of fertility and harvest. Nowadays, when idolatry is practiced in a more purified and concentrated way, the worship of money is a god of choice for many who don't look to the true God to both supply their needs (in the black) and also to cover their sins (in the red). "In the black" might be good for business but check your heart. When standing before God, no one wants theirs that color.
"For what shall it profit a man, if he shall gain the whole world, and lose his own soul? Or what shall a man give in exchange for his soul?" (Mark 8:36-37)
In the White
"He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels." (Revelation 3:5)
Snowblindness happens when you stare at snow in direct sunlight. It's so bright that without special glasses the eyes are injured from the intense whiteness. And that's the best that this earth can do as far as white. But the whiteness of Heaven? Quoting the angel Zauriel from the JLA: "Only spirit can bear Heaven's touch." Well said for a comic book character.
"And they overcame him by the blood of the Lamb, and the word of their testimony; and they loved not their lives unto the death." (Revelation 12:11)