One of the many titles given to Jesus Christ is that of the Great High Priest (see Hebrews 5). To understand this Messianic title, we first must understand the role and significance of the High Priest in ancient times. During the exodus, as the Israelites were camped at the base of Mount Sinai, the Lord desired that all his children be able to enter into his presence within the walls of the Temple or Tabernacle. However, because of their sinfulness in creating a golden calf, God instead had the High Priest take the place of Israel, becoming the intercessory on their behalf. To help symbolize his important role as a mediator and as a type of Christ, each piece of the clothing of the High Priest pointed to the Messiah.
"The high priest wore eight holy garments. Of these, four were of the same type worn by all priests, and four were unique to the High Priest." 
The four garments worn by all priests were, first, the priestly undergarments or breeches. These linen pants were made to "cover the nakedness" of the priests and covered them from the waist to the knees (Exodus 28:42). Second, was the priestly tunic or robe, which was likewise made of white linen, was seamless, and covered most of the body of the priest (Exodus 28:39-40). Third, was the priestly sash, made of white linen for the normal priest, and an embroidered sash made of gold, blue, purple, scarlet, and white for the High Priest, and was used as a type of belt around the tunic or robe. Fourth, is the priestly turban, bonnet, or cap, which was a long strip of white linen wrapped around the head of the priest.
|The blue robe with alternating golden bells and pomegranate-shaped tassels|
|The white robe and turban used by all priests|
On the blue outer robe were attached alternating bells and pomegranate tassels. As the High Priest would walk around the bells would ring, reminding everyone around him, that they were in the presence of the High Priest, the representative of the Lord. The pomegranate in the scriptures represents fruitfulness, posterity, and prosperity, as there are literally hundreds of seeds in a single fruit. It is through the atonement of the Messiah that we are all made children of Christ, and heirs of his kingdom.
"In the scriptures ... the forehead represents what a person’s thoughts dwell on and therefore what he loves or desires. ... For the same reason, the Mosaic high priest wore an engraved gold signet on his forehead that read ‘Holiness to the Lord’ (see Exodus 28:36-38). This was a reminder that his thoughts should always be holy, with the result that his actions would follow suit." 
|The clothing of the High Priest|
|Close-up of the breastplate showing the five colors|
Gold in the scriptures represents wealth, power, the celestial realm, and the divine.  Blue represents all things heavenly, being the color of the sky. The priest's outer robe being entirely blue "emphasized the fact that his authority was of heavenly origin and his life was the typifying of God and Christ."  The color purple represents royalty, power, wealth, and majesty. Producing purple dye in ancient times was extremely costly and difficult, meaning that only the wealthiest could afford to wear the color purple.  It is interesting to note that Christ, according to Mark and John, was clothed in a purple robe by the soldiers before his crucifixion in an effort to mock him as the King of the Jews (see Mark 15:17 and John 19:2-3). The color scarlet, or red represents sin, mortality, death and resurrection.  In the same account of the mocking soldiers, Matthew tells us that the robe was scarlet (see Matthew 27:28). In addition, the book of Revelation depicts Christ at His Second Coming wearing a robe dipped in blood, making it the color red (see Revelation 19:13). As was already mentioned, white represents purity and typifies the type of life that Christ lived.
|The breastplate of the High Priest|
As Paul wrote, "Seeing then that we have a great high priest, that is passed into the heavens, Jesus the Son of God, let us hold fast our profession. For we have not an high priest which cannot be touched with the feeling of our infirmities; but was in all points tempted like as we are, yet without sin. Let us therefore come boldly unto the throne of grace, that we may obtain mercy, and find grace to help in time of need." (Hebrews 4:14-16). 
 High Priest of Israel, Wikipedia
 High Priest of Israel, Wikipedia
 Linen, BibleStudyTools.com
 Revelation 15:6 speaks of the seven angels being likewise clothed in white linen
 The Lost Language of Symbolism, by Alonzo L. Gaskill, page 39 (see Forehead)
 The Lost Language of Symbolism, page 91-93 (see Gold)
 The Lost Language of Symbolism, page 89-90 (see Blue)
 The Lost Language of Symbolism, page 96-99 (see Purple), also see Esther 6:7-8, 8:15 when Mordecai is dressed in a purple robe to represent the royal favor of the king.
 The Lost Language of Symbolism, page 99-102 (see Red/Scarlet)
 The number 5, The Bible Study Site
 The book of Hebrews mentions the term 'high priest' 20 times, and is by far the best scriptural source for teaching about the relationship between the High Priest and Jesus Christ.