Different eras have different color associations, and different languages have different definitions of color range. That makes meaningful discussion of color symbolism a bit difficult.
So first off, I agree that when Mary wears red robes, in the West it is associated with showing her humanity, while in the East it represents nobility or royalty. (So does imperial purple (which is red or reddish-purple), which is another common color for her robes in Eastern icons.) As a queen mother of the House of David, this is Mary’s right.
And before you say that wearing red robes is a sign of being a slut, you should ask yourself why Jesus wears red robes in the Old Testament. Hint: it has something to do with blood and kingship and wine, not with Him being a slut.
But the real question you should be asking yourself is —
What color is “scarlet” in the Book of Revelation?
John uses the Greek word “kokkinon,” which is the dye color “crimson,” produced by kermes bugs when ground up into a powder. It produces a deep red with overtones of purple. This color was very prized in Roman times, though not as much as Tyrian purple (which was actually a red-purple, but I digress).
“Scarlet” is a different color, much more like an orange-red. Translators use “scarlet” for its associations in English, not because it’s an accurate translation. In John’s time, there was no such word as “scarlet;” Romans and Greeks called the color “Armenian red.”
(She really does wear “porphyroun,” though, which is the red-purple porphyry color associated with Roman and Byzantine emperors.)
And why is the harlot wearing purple and scarlet, just like she’s wearing a crown and riding on a Beast that symbolizes a bunch of kings?
Because she’s Roma Mater, the imperial city that ruled the Roman Empire in John’s time, the city that was worshipped as a goddess by emperors and common people alike. So she dresses like an empress. (Calling her “Babylon” is pretty much a giveaway, as Babylon had once been the center of a great pagan empire.)
One of the big points of Revelation is that there’s Jesus, the real King of Heaven and Earth, and then there’s the devil and the Antichrist, who are doing their darndest to usurp Jesus’ rightful place in people’s hearts and actions. Likewise, there’s the good Woman and the Bride, and then there’s Jezabel the bad teacher (in the letters to the churches) and the Great Harlot, who are trying to take their place in people’s hearts and actions.
So if you want to complain that Mary wears rich colors and so does the Great Harlot, you will also have to take into account that Heaven is full of golden vessels, just like the Great Harlot’s golden cup.
The point is that you can’t trust in earthly kings and princes and cities, even if they do have gold crowns and purple robes. You can trust in the King of Heaven, Who was royal even when His apparel included blood, a crown of thorns, nails, and a cross.
