Well, the Seraphim are the highest choir of angels.. they are the closest angels to God and worship Him and experience the fires of His love by nature most closely.. (not accounting for any perhaps changes of position due to other graces) and are most notable for the fires of their love of God.. ...
So they are the royalty of royalty of the angels..
Purple is used in the veil around the tabernacle..
Mary is often equated with the tabernacle itself.. then Christ within..
In the year that king Ozias died, I saw the Lord sitting upon a throne high and elevated: and his train filled the temple. Upon it stood the seraphims: the one had six wings, and the other had six wings: with two they covered his face, and with two they covered his feet, and with two they hew. And they cried one to another, and said: Holy, holy, holy, the Lord God of hosts, all the earth is full of his glory. And the lintels of the doors were moved at the voice of him that cried, and the house was filled with smoke.
And I said: Woe is me, because I have held my peace; because I am a man of unclean lips, and I dwell in the midst of a people that hath unclean lips, and I have seen with my eyes the King the Lord of hosts.
And one of the seraphims flew to me, and in his hand was a live coal, which he had taken with the tongs off the altar. And he touched my mouth, and said: Behold this hath touched thy lips, and thy iniquities shall be taken away, and thy sin shall be cleansed. And I heard the voice of the Lord, saying: Whom shall I send? and who shall go for us? And I said: Lo, here am I, send me. And he said: Go, and thou shalt say to this people: Hearing, hear, and understand not: and see the vision, and know it not. Blind the heart of this people, and make their ears heavy, and shut their eyes: lest they see with their eyes, and hear with their ears, and understand with their heart, and be converted and I heal them.
Isaias 6:1-10
Lydia I have just read some commentary on saying was St. Paul's first convert to Christianity in Europe. And that since Paul and his companions stayed and prayed at her house, it could even be considered the first Christian church in Europe.
'Therefore, my dearly beloved brethren, and most desired, my joy and my crown; so stand fast in the Lord, my dearly beloved.'
Philippians 4:1
4:1
The Philippians are St. Paul's joy and crown.
Lydia's name is in reference to a place, I have read, so it's difficult to pursue any particular meaning to her name beyond as far as I can tell - that which normally is what helps uncover more of the meaning of many passages in scripture.
Hmm I see her listen in the Patron Saints' Index as 'Saint Lydia Purpuraria' (meaning purple seller)