Having not grown up Catholic, when I first attended a Catholic Church, one of the things that caught my attention was the way the priest was dressed. I was accustomed to a minister either dressed in a business suit, or in academic robe. Being the 16 year old that I was, I immediately asked the man who would be my "padrino" in Nicaragua, "What's that about?" followed by, "Where is that in the Bible?"
He patiently walked me through each vestment, beginning with the most important, the alb. It is the first one you put on. The word alb in English comes from the Latin word for white. It is the white garment of baptism. It is not reserved to the priest; it can be worn by any baptized Christian. It's job is to remind us who we are.
The the Galatians reading today we hear,
For through faith you are all children of God in Christ Jesus. For all of you who were baptized into Christ have clothed yourselves with Christ.
In the rite of baptism we bless the white gown on the person baptized with the prayer,
you have become a new creation,
and have clothed yourself in Christ.
See in this white garment the outward sign of your Christian dignity.
With your family and friends to help you by word and example,
bring that dignity unstained
into the everlasting life of heaven.
Every minister from the altar server to the Pope wears the same white garment.
At the end of mass we may take off the alb, but we should never take off Christ.
There is an old saying, "The clothes make the man." In this case it is true. At baptism we are clothed in Christ, and that clothing should be constantly changing us more and more into his image.