Using RGBA in other then what made for

Many people think that RGBA only used with image pixel information and to define the color of an image. But  idea of RGBA can be used to hold masks, depth values, xyz and some other things. when render out form 3D software, in case that it needed some masks for the objects in the scene so it will be easy later to edit in compositing software, use RGBA to hold these masks by assigning these colors to the objects then render it out as a normal image. (red, green, blue, black, white) (be sure not to assign same color to object next to each other). also RGBA can hold XYZ values, which can be very helpful in compositing software. can be use in color correction, relighting, position 2D object in relation the 3D object...so on.