Halos are light areas around light sources, used to give the impression of small dust particles in the air.
Color of the Halo.
Size of the Halo.
You can add a Halo component to a Light object and then set its size and color properties to give the desired glowing effect. A Light component can also be set to display a halo without a separate Halo component by enabling its Draw Halo property.
To see Halos in the scene view, check Fx button in the Scene View Toolbar.
To override the shader used for Halos copy the Internal-Halo.shader shader from the Built-in shaders into a folder named “Resources” in your “Assets” folder.