Is the colour which represents penance.  The two Penitential seasons in the church calendar are Advent (the four weeks prior to Christmass), and Lent (the six weeks prior to Easter).

Is the colour we use to mark festivals and feasts.  The major feasts are Christmass and Easter, but these colours are used also for other times of the year such as the Epiphany, Corpus Christi, Christ the King, and saints (except those saints who were either apostles or martyrs).

Is the colour for the Sundays after Trinity, or what we now call 'Ordinary Time'.  It is really the general season of the year, the colour we use when there is nothing particular going on, if you like! 

Is the colour we use for saints who were martyrs or apostles.  We also use red for Pentecost Sunday (where the red is the symbol of fire and the Holy Ghost), and also for Good Friday.  Red is also used for Palm Sunday, and in some churches red is then used right up until the Easter Triduum, although strictly after Palm Sunday purple is used inclusively until Maundy Thursday (gold) and then Good Friday (red).

Is the colour we use for Christian burial, and for Requiem masses (or masses of the dead).  It is also permissible, and perhaps more common now that purple is used for this purpose, and in some places white is used for requiems to symbolise the Resurrection.  Although this is far less common than the use of purple and black, for requiems and burials of children, white is used exclusively.

Is used for Our Lady (St. Mary).  Great feasts of Our Lady such as the Assumption, The Annunciation and so on are times when blue might be used - and for Our Lady on Saturday.  Gold and white are also permissible for Our Lady, and are in fact more common.

This colour is used for just two Sundays in the year.  The 3rd Sunday of Advent, and the 4th Sunday of Lent (Mothering Sunday).