'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)

9002. 'If he takes another one for himself' means being joined to an affection for truth stemming from some other source. This is clear from the meaning of 'taking (or betrothing) another' as being joined to, as in 8996; for in the spiritual sense marriage, which is implied here by betrothal, is the joining of the life of one to that of another. Divine order decrees that the life of the truths of faith and the life of the good of charity should be joined together; this is where all spiritual joining together begins, from which, as its origin, natural joining springs. 'Taking another one' means being joined to an affection for truth stemming from some other source, because 'a female slave', dealt with before, is an affection for truth springing from natural delight, 8993, and therefore 'another one' is an affection for truth stemming from some other source

[2] An idea of what an affection from some other source is may be gained from the consideration that every affection belonging to love is very broad and wide indeed, so broad that it extends far beyond all human understanding. Human understanding cannot go so far as to know even the genera of the varieties of such affection, still less the species making up the genera, and least of all the particular aspects and individual details of those aspects. For all that exists within the human being, especially that which belongs to affection or love there, is infinitely varied. This becomes perfectly clear from the consideration that the affection for what is good and true, an affection that belongs to love to the Lord and love towards the neighbour, constitutes the whole of heaven, and yet in respect of good those in the heavens, where millions live, are all different from one another. And they would still all be different even if multiplied into countless millions of millions. For it is not possible in the universe for one thing to be exactly like another and have separate existence. It must vary, that is, be different from another, if it is to be something by itself, see 684, 690, 3241, 3744, 3745, 3986, 4005, 4149, 5598, 7236, 7833, 7836, 8003. All this gives some idea of what one should understand by an affection from some other source, namely an affection which is different from another but can nevertheless be joined to the same spiritual truth. Such affections, which are represented by female slaves betrothed to the same man, belong to the same genus but different species, the difference between them being called a specific difference. Various examples could be used to illustrate these matters; but the general idea conveyed by the things that have just been said is better.

[3] So that the joining of such affections to the same spiritual truth, and their subordination to it, might be represented, it was permissible within the Israelite and Jewish nation for men to have a number of concubines. Abraham had them, Genesis 25:6, and so did David, Solomon, and others. For anything permitted among that nation existed because of what that thing represented; or to be more precise, it existed so that by means of outward things that nation might represent the inner realities of the Church, 3246. But when the inner realities of the Church were disclosed by the Lord, representations of inner realities through outward things came to an end; for now it was the inner realities - forms of faith and love - that were to be apprehended by a member of the Church and to be the means by which he worshipped the Lord. For this reason they were no longer permitted to have a number of wives, or concubines as well as wives, see 865, 2727-2759, 3246, 4837.