Green is used for Ordinary Time / The Season after Pentecost / Trinitytide / Gracetide (depending on your terminology) to represent the continual growth in the faith that we are to pursue during this time.
Violet/Purple for Advent and Lent are both somewhat penitential in our modern thought but originated as Kingly (i.e., royal) colors - a mark of the King, coming through Mary at Advent, Coming to Jersusalem during Lent. Ideally the Lenten vestments should be a darker violet with a more reddish hue if the Church can afford more than one set of vestments in Violet. The Advent set should hue more towards an indigo color.
In some places, though currently forbidden in the Roman Rite (with very few exceptions) blue has been used for Advent. It was common practice in England from the 9th to 14th Centuries. It remained a popular custom in Scandanavia, and it is from Scandanavia that this custom has begun to re-enter some Churches. In the Roman Rite, blue for advent is forbidden, but blue is permitted in some places as a liturgical color for the Blessed Mother. Generally these are referred to as, if I recall correctly, Spanish Privilidge, and thus in the USA it is not normative or used. (Of course, that doesn’t stop local pastors from violating the GIRM, but, well… what does?)
Rose (not pink

) is actually the third candle on the Advent Wreath. Rose vestments may be worn on the Third Sunday of Advent and the Fourth Sunday of Lent. These ‘refreshment Sundays’ as they have been popularlly known, are actually set apart as days of slightly lighter discipline with regards to the Sunday celebration (ur… at least they were under the Tridentine Rite). The organ, which was generally silent during Lent, was permitted on these days, as were tasteful but limited flowers. In the Church of England, even after her break from Rome, while the Liturgical colors eventually disappeared, this particular Sunday of Lent became known as Mothering Sunday, and - as a result - was always a bit of a joke as a Lenten Sunday. But I digress…
There are two shades of Red that are commonly used, though in modern usage most parishes just have one set of red vestments.
Oxblood, a deep dark red, also known as Passiontide Red, is used for Palm Sunday, Good Friday, and in some places (though not the Roman Rite) for Holy Week. At one time, Passiontide vestments were worn throughout not only Holy Week but also Passion Week (the 5th Week of Lent). This was a popular custom in England, Scandanavia, and some parts of Portugal. These vestments are also worn on the Feasts of Martyrs, and symbolize the blood of Christ and the Martyrs. Most parishes don’t spend money on these, however, so…
Red Vestments - bright! - are used for Pentecost (and the Octave of Pentecost in those places where Pentecost is still observed with an Octave) as a reminder of the fire of the Spirit. They are also used for confirmations and ordinations (though, in many places, white vestments are prefered for Ordinations). They are also substituted for Oxblood vestments when they cannot be had.
One other thing, essentially unused and unheard of in the United States, is the Lenten Array. It was an English custom to use unbleached linen and sackcloth together with oxblood and ash (dark gray or black) ophreys (strips of ornamentation) for vesting the clergy, the altar, the ambo, etc… until Passiontide. It was a symbol of abasement, fasting, and penance. This custom enjoyed a resurgence in the 1890s, first among the Tractarian/Oxford Movement Anglicans, and then among other Liturgical Churches in England. While many American Anglicans took it up, the practice never did come into vouge with American Catholics. For an example of a Lenten Array:
home.vicnet.net.au/~ccb/lenten_array.html
Hope this was helpful,
Rob+