This picture shows two thing in one picture, the battle of the living and the dead. The blue side is the side of dead army, and the other side of red and orange represents the side of living army.
The night king is riding on Ice Dragon (former Viserion Dragon). And Daenerys Targaryen is riding Drogon (one of her Dragons). The Battle of Winterfell is the final battle of the Great War between an alliance of living armies, including the forces of the Starks, Arryns, and Targaryens, against the army of the dead led by the White Walkers. The battle takes place at Winterfell, the seat of House Stark and regional capital of the North. In fact, it was reportedly the longest battle sequence in cinema history.