Looking at artwork from the Middle Ages, it is evident dragons haven’t always been four legged scaly winged beasts. They often appear to not have their front pair of legs, and are more similar to serpents – some don’t even have wings! It derives from the Greek term ‘drakon’ meaning “serpent of huge size, water-snake”. This suggests historically dragons have always been viewed as mythical snakes rather than four-legged beasts, but variations differ. One thing that seems consistent in most artworks of St. George and the Dragon is that it is green rather than red; unusual considering something bad is usually thought of as being red – an association that may have developed since the medieval times. Perhaps the green colour comes from the colour of the wilderness – a place feared in the Middle Ages considering it was home to wolves and wild boar in areas which are now barely residence to a wood pigeon. Imagery of red dragons in more recent artworks possibly come from Welsh influence in which a red dragon is seen on their flag and is part of their folklore. Dragons in the Middle Ages existed as little more than a Christian symbol, but they have existed around the world with many other meanings for many previous centuries.
Please note the information above is given from personal judgement of contemporary artworks and re-iteration of other secondary sources. It may not be factually correct although it is often a reasonable judgement.