Silvertide, celebrated on the 14th of Lharvion (July), honors the couatl who make up the Silver Flame. This midsummer holiday is a joyous celebration of a world that was unshackled from demonic rule aeons ago. The advent of affordable paint in the eighth century introduced a new element to the holiday—rainbow paint fights. Throughout the day, communities are splattered with a special paint manufactured in Athandra. At dusk, however, the local priest transmutes the paint into silvery dust, symbolizing the valor of the couatl and the significance of their sacrifice to kindle the Flame.
Source: Cultures of Thrane
The 14th of Lharvion is Silvertide, one of the holiest days for followers of the Silver Flame. It celebrates victory against the overlords in the Age of Demons and commemorates the sacrifice of the couatl to form the Silver Flame. In some of the smaller communities, Silvertide is celebrated by having a village-wide paint fight, painting the community and its members in the rainbow colors of the couatl, before the local minister performs a ritual to turn all the paint to silver, emulating the forging of the Flame by the couatl.
Source: Sarhain's Guide to the Silver Flame
This highest holy day of the faith celebrates the sacrifice of the couatls and the birth of the Silver Flame.
Source: Eberron Campaign Guide
The highest holy day in the faith, Silvertide commemorates the sacrifice of the couatl and the entry of the Silver Flame into Eberron thousands of years ago. Cathedrals fill to overflowing as all Purified who do not absolutely have to be somewhere else spend the day in prayer and observance.
Source: Faiths of Eberron