PDF (adobe.com)

Light attributes and methods

Light objects have the same attributes and methods as Layer objects, except for source, effect, mask, width, height, anchorPoint, scale, opacity, audioLevels, timeRemap, and all of the material properties.

pointOfInterest
Return type: Property [3].

Returns the point of interest values for a light in world space.

intensity
Return type: Property.

Returns the intensity values of a light as a percentage.

color
Return type: Property [4].

Returns the color value of a light.

coneAngle
Return type: Property.

Returns the cone angle of a light, in degrees.

coneFeather
Return type: Property.

Returns the cone feather value of a light as a percentage.

shadowDarkness
Return type: Property.

Returns the shadow darkness value of a light as a percentage.

shadowDiffusion
Return type: Property.

Returns the shadow diffusion value of a light, in pixels.

David Van Brink provides an instructional blog post and sample project that show how to use expressions with lights: www.adobe.com/go/learn_ae_ominoflashing.