Today, I happened to be out and about with my camera just as the Palm Sunday observance was about to begin at Our Lady of Perpetual Help.
According to Catholic Online:
During Palm Sunday Mass, palms are distributed to parishioners who carry them in a ritual procession into church. The palms are blessed and many people will fashion them into small crosses or other items of personal devotion. These may be returned to the church, or kept for the year.
Because the palms are blessed, they may not be discarded as trash. Instead, they are appropriately gathered at the church and incinerated to create the ashes that will be used in the following year's Ash Wednesday observance.
The colors of the Mass on Palm Sunday are red and white, symbolizing the redemption in blood that Christ paid for the world.