'Scarlet,' as in Genesis 38:28, signifies spiritual good.

In Isaiah 1:18, this signifies truth derived from good, or truth from a celestial origin, such as is the truth of the Word in its literal and natural sense

'Scarlet,' in Revelation 17:3, signifies truth from a heavenly origin, such as is the truth of the Word in the sense of the letter or natural sense, which is meant by what is holy in it. 

(Odkazy: Apocalypse Explained 67)

1619. THE LIGHT IN WHICH ANGELS ARE LIVING - continued; ALSO THEIR PARADISE GARDENS, AND THEIR DWELLING - PLACES

When a person's interior sight - the sight of his spirit - is opened, he then sees things in the next life, things that can never be manifested before his bodily eyes. The visions that the prophets had were nothing else. As has been stated, representatives of the Lord and of His kingdom, as well as meaningful signs, are to be seen constantly, so much so that nothing ever comes before the eyes of angels that is not a representative or a meaningful sign. This is the origin of representatives and of meaningful signs in the Word, for the Word derives from the Lord through heaven.