Ask and you shall receive! Marty, this one's for you. :)
So, in divinity school I had a professor whose specialty was the history of Christian worship. And he told us that the most basic meaning behind the candles on the Advent wreath is ... 1,2,3,4. It started out as simply counting down (up?) to Christmas, marking the time. And of course, the Christ candle for Christmas works very well with all the "Jesus the Light of the World" imagery.
But that professor also liked to talk about how symbols "aren't like stop signs," that is, they are not limited to one single meaning. And meanings get added in layers over time ... this is probably true about most of the things that happen in church (and many things that have nothing to do with church).
When I was growing up, both my dad's Catholic and my mom's Disciples churches had themes for each week of Advent, and included lighting the Advent wreath as part of each Sunday's worship. The themes were, in order: Hope, Peace, Joy, and Love. Joy, the third Sunday, went with the pink candle, and the white Christ candle was in the middle. In my mom's church, a different family lit the Advent Wreath each week, and read some Scripture, a prayer, and a brief reflection on the meaning of the particular week. I remember my mom getting a little stressed about people lighting the candles in the correct order. (You have to start with the purple candle that's across from the pink candle to get to the pink one at the right time.)
We also often had an Advent wreath at home -- subsequent Internet research suggests to me that we were participating in a Catholic movement to integrate the faith into the homes of Catholic families. Another way to say that is that my dad brought a booklet home from his church and my mom liked the idea so she got a wreath, and we lit the candles at dinner during Advent sometimes. This scheme (3 purple candles and one pink on the outside, white in the middle) has roots in the time when Advent was a small fast, a time of reflection and penitence, a sort of echo of Lent -- hence the color purple. The pink candle and Joy, however, represent a disruption of the fast, a celebration. (Not unlike Sundays being little Easters during Lent.)
When I was serving as a pastor at Cleveland Park Congregational UCC, I did some research to put together liturgy for our wreath-lighting that was consistent with the New England Congregational tradition of the four candles representing: Faith, Hope, Love, and Joy. In this scheme, the outer candles would all be the same color. Purple is certainly appropriate, but blue, red, or even white are also possibilities. The aforementioned internet research suggested that most places where this tradition is preserved (insofar as it is discussed online) are Unitarian churches. I also discovered another scheme for the candles that I liked: Prophets, Bethlehem, the Shepherds, and the Angels. There are actually a lot of possibilities.
I think that whatever the significance attributed to each of the candles, it's a challenge to make the themes of Advent fresh in some way each year at the same time as you preserve ancient tradition. Because I have some fond memories of Advent wreaths, and, ahem, have done perhaps too much internet research, and because a few years ago I found an Advent wreath on sale at my favorite fair trade store, we have one, and some years, I have imposed dinner table Advent wreath lighting on my family. The candles are all purple, which I decided, based on, yes, my internet research (as well as that divinity school education!) was theologically sound.
We have the Advent wreath and candles here with us in Nicaragua, and I like the opportunity to celebrate Advent a little, to have a simple ritual that's part of our home life that Quinn can relate to. Her favorite part, of course, is blowing out the candle, probably because of all the recent blowing out of birthday candles (she got to blow out the birthday candles on her cake on 3 occasions this year). My plan is to do it just once a week during Advent (the candles last longer that way :) ), and we actually remembered to on Sunday, when Advent began. It is nice to have a little bit of home and family tradition in the midst of so many changes and differences. So, to sum up: I have spent really a lot of time researching Advent wreaths on the internet, and I like them.