The $3 stamp (above left) prepays the difference between the overnight rate and the same day rate. It shows a red poppy flower. The red poppy is an internationally recognized symbol of fallen soldiers in battle. This came about after the poem "Flanders Fields" by Lt. Col. John McCrae in 1915 which mentions red poppies growing on the graves of buried soldiers (see FDC cachet). Full text of the poem below:

In Flanders Fields the poppies blow
Between the crosses row on row,
That mark our place; and in the sky
The larks, still bravely singing, fly
Scarce heard amid the guns below.
We are the Dead. Short days ago
We lived, felt dawn, saw sunset glow,
Loved and were loved, and now we lie
In Flanders fields.
Take up our quarrel with the foe:
To you from failing hands we throw
The torch; be yours to hold it high.
If ye break faith with us who die
We shall not sleep, though poppies grow
In Flanders fields.

The $6 stamp (above middle) prepays the Overnight rate. It shows two views of the Punchbowl cemetery in Honolulu. The statue of Lady Liberty which stands at the top of the steps overlooking the National Memorial Cemetery of the Pacific. Also shown is one of the graves that Lady Liberty overlooks. In this case, it is of an unknown sailor or civilian who died in the Japanese attack on Pearl Harbor on December 7, 1941.

The $9 stamp (above right) prepays the Same Day rate. It shows the Waikiki Natatorium. This was built in memory of the soldiers from Hwai'i who died in World War I. It is now in disrepair awaiting its fate by the City and County of Honolulu as to whether to renovate it or demolish it.

Memorial Day is an annual federal holiday in the USA and held on the last Monday in the month of May. It is a day to remember those men and women who died while serving in the US Armed Forces. Traditionally on Memorial Day wreaths and flowers are laid on the graves of fallen soldiers.