I think this isn't an official webGL effect. Anyway, there isn't that complicate to figure it out. The first 3 parameters are shifting the RGB colors that compose the image on the X axis, the next 3 parameters are doing the same for the Y axis and the last one controls how much of the above will be shown.
If you apply the effect on the sprite, it will be bound to the spite's own dimensions (it will not "bleed out" color beyond its actual borders). If you apply the effect on a layer however, it will spread the RGB colors of each and every sprite on that layer around.
The way it shifts the colors is a bit strange though.
If you push the Red color 100 px on the right (when applied on a layer for example), it will create an image without the Red channel 100 pixels on the right (a bluish image like having only the G+B channels), and keep a reddish image in place. (The same thing will happen for any individual channel.) If you add to that a 50 px shift on the green channel, you'll get a second, purplish image 50 px away (as a combination of the R+B channels) and you will be left with a yellowish image in place (as if having the R+G channels)...
I know, it's weird... It renders interesting "damage" effects when used subtly though.