While earlier Star Wars movies have shown blood on a few occasions, like when Obi-Wan Kenobi sliced off Ponda Baba's arm in A New Hope, for the most part this series has stayed away from being gory. In order to not break this trend in The Last Jedi, Rian Johnson decided to have the mineral coating Crait's surface highlight the violence that unfolded between The Resistance and The First Order. When all is calm, Crait's landscape is the smooth white, but when The Resistance's ski speeders started kicking up the mineral and the laser blasts started flying, then it turned into this "hellscape." Johnson also mentioned to /Filmcast that the idea of red streaks standing out against the white salt planet was a "visual that came about very early," but more importantly, he was able to use said visual to effectively show how war is hell, even in a galaxy far, far away.