How could the Christian crusaders be recognized among all the warrior fighting in the crusade?

They wore heavy suit of armor.

Explanation:

They wore heavy suits of armor. They rode black horses. Their tunics had a large, red cross on the front.

The Crusades were organized by western European Christians after centuries of Muslim wars of expansion. Their primary objectives were to stop the expansion of Muslim states, to reclaim for Christianity the Holy Land in the Middle East, and to recapture territories that had formerly been Christian.

here were eight major official crusades between 1095 CE and 1270 CE and many more unofficial ones, none would be as successful as the first, and by 1291 CE the Crusader-created states in the Middle East were absorbed into the Mamluk Sultanate.