Why are the poppies used for Remembrance Sunday coloured red?

Red poppies symbolise remembrance.

The story goes that, following one of the bloodiest battles of World War I, in the fields of Flanders in Western Europe,when the ground was completely churned up and muddied, thousands of red poppies sprang up. The seeds had lain dormant in the soil and, after being aerated with the churning of the soil from the soldiers' boots and fertilised with their blood, the poppies grew abundantly, springing forth new life from death.

This is why poppies are worn on Remembrance Day (commemorating Armistice Day) as well as ANZAC Day in Australia and New Zealand, and other solemn occasions when we remember the soldiers who fought or even gave their lives for our freedom.

Another reason poppies came to such prominence in association with World War I is because of how they were immortalised in that most famous poem of WWI, In Flanders Fields, written by John McCrae, a Canadian surgeon attached to the 1st Field Artillery Brigade. This poem is spoken at memorial services everywhere on both ANZAC Day and Remembrance Day, and remains one of the most famous Australian War poems ever written.