i only know the gospel of luke's written by a greek doctor. and
seems to speak more to pre-believers. and the gospel reflects
Jesus, the sinless man.
Matthew: purple (representing royalty) - Jesus the King -
intended to be read by jews
Mark: red (representing sacrifice) - Jesus the servant -
intended to be read by gentiles
Luke: white (representing purity) - Jesus the sinless man -
intended to be read by gentiles
John: blue (representing divinity) - Jesus the Son of God
4 colours which are used in making the garments for the high
priests in Exodus
28
http://campus.houghton.edu/orgs/rel-phil/schultzweb/priestly.htm