var('x','y','z')

p1 = implicit_plot3d(x+y == 0, (x,-3,3),(y,-3,3),(z,-3,3))
p2 = implicit_plot3d(z+y == 0, (x,-3,3),(y,-3,3),(z,-3,3),color="red")
p3 = implicit_plot3d(x+z == 0, (x,-3,3),(y,-3,3),(z,-3,3),color="purple")
show(p1 + p2 + p3, viewer='threejs')