In the comments, Songbird raises a question
related to the use of blue or purple candles for the Advent wreath.  Why,
she wonders, has there been some shifts toward blue rather than purple.
Because I wanted to be as accurate as I can in my response, I did a
little research.  And I intend to do a little more, but here’s what I
found out so far.

Purple, in the Catholic Church, is
the prescribed color for the vestments used during both Advent and Lent.
There is no mention of blue in the documents which are intended to help us, as
a communion, celebrate the liturgical seasonsin communion with one another and
the whole church.

Protestant churches and
communities, however, experience more freedom in their choices of celebratory
vestment colors.  And so, for many protestant communities, the shift
indicates, among other things, a desire to differentiate the penitential nature
of the Lenten season (and the purple color used to express it) with a
"spirit of expectation, of anticipation, of     preparation, of
longing." (Dennis Bratcher)
And so using a deeper purple, an indigo or more "blue-ish" purple may
sometimes be chosen.

In the Catholic Church, which as I mentioned is more regulated in its worship, the Advent Wreath is not a strictly liturgical element.  It is "a pious practice that is not regulated by the Church as the liturgy is.  However, if it is thought that the candle colors should be that of the sacred vestments, purple or violet, not blue, should be selected." (Eric Stoutz)

to some Catholics, the desire to have the wreath match the vestments, overrides
the desire to represent a spirit during Advent that is different from the
spirit with which we celebrate Lent.  And to other Catholics, the use of a
deeper purple for Advent (and purple as a secondary color is almost always
rooted in blue), is chosen to represent that spirit of expectation,
anticipation and longing.  It’s a time to prepare ourselves, which does
indeed invoke a personal and communal practice of penance, for the next coming
of Christ.  (I like to think the next coming of Christ is not only the
Second coming, but also the next time I, in wisdom and humility, actually
welcome Christ into my heart and life: a process that is repeated daily,
weekly, sometimes hourly…)

Personally, I prefer the blue-ish
candles; the deep rich purple, the indigo, reminds and evokes for me the night
into which Jesus was born.  The night of the world, the night of the
stable, the night of my heart.  I adore the Lenten violet as well; but it
does hold a different spirit.  Maybe because I came back to the Catholic
faith in a community that used indigo in the candles and some of the
environment cloths, maybe that is why it holds the spirit of Advent so clearly
for me.  Maybe I just like more color, any way I can get it.  I was
on the liturgy planning team for a few years at that former Catholic community
and we had many discussions around this.  We were interested in providing
the deepest, most personal, most communal, most significant, most holy
experience for the members of our local community and for the many guests who
would visit us during the holidays.  And we, at least at that time,
thought using a distinguishing color for the candles and decor was
appropriate.  It stuck with me.

All that being said, I need to go
set up my Advent wreath for tomorrow!  Blessings on you and yours!

We live always during Advent. We are
always waiting for the messiah to come. The messiah has come, but is not
yet fully manifest. The messiah is not fully manifest in each of our
souls, not fully manifest in humankind as a whole: that is to say, that just as
Christ was born according to the flesh in Bethlehem
of Judah,
so must he be born according to the spirit in each of our souls.
– Jean Danielou