The red cross that became representative of the Templar Knights was given to them as a symbol for their order by Pope Eugenius III in 1147. The type was a cross pattée and was a variation on the "Mark of Cain" minus the circle. The red cross itself was a symbol of martyrdom. Yet it was an imposing visual first seen in battle in the second crusades and continued in the two that followed.
Years earlier Jesus first encountered the "Mark of Cain" in his extensive travels when the Celtic Druids of Glastonbury showed him their Celtic Cross. Later Jesus would introduce followers or early Christians to the Sign of the Cross. A person would simulate the cross by touching their forehead, chest and both shoulders. He taught about balancing the mental and emotional energies and touching the head activated the mental energy, touching the chest where your heart is activates the emotional energy and touching both shoulders signals the full activation of both energies.
Templar Knights page