I am trying to make a simple bot for a web game, so I would like to be able to read the color of a pixel on the screen. I've done this on Windows with GetPixel, but I can't seem to figure it out on OS X. I been looking online and came across glReadPixel. When I made a simple command line tool in XCode, I put in the following code. You can use the inspector to view information about a document or image, such as file size, the author’s name, and the image resolution. In the Preview app on your Mac, open a PDF or image that you want to view. Choose Tools Show Inspector, then do any of the following: Get general file information: Click the General Info Inspector button.
ActorPositionWS
ActorPositionWS outputs Vector3 (RGB) data representing the location of the object with this material on it in world-space.

In this example, you can see that ActorPositionWS is being fed directly into the Base Color of the material. As a result, each of the spheres with the material applied to them show a different color as they are moved to different locations in 3D space. Note that the result of the ActorPositionWS node is being divided by 1600 to create a nice blend-in color, rather than a pop.
CameraPositionWS
The CameraWorldPosition expression outputs a three-channel vector value representing the camera's position in world space.
The preview sphere changes color as the camera rotates.
LightmapUVs
The LightmapUVs expression outputs the lightmap UV texture coordinates in the form of a two-channel vector value. If lightmap UVs are unavailable, it will output a two-channel vector value of (0,0).
ObjectOrientation
The ObjectOrientation expression outputs the world-space up vector of the object. In other words, the object's local positive z-axis is pointing in this direction.
ObjectPositionWS
The ObjectPositionWS expression outputs the world-space center position of the object's bounds. For example, this is useful for creating spherical lighting for foliage.
ObjectRadius
The Object Radius outputs a value equal to the radius of a given object in Unreal units. Scaling is taken into account and the results can be unique for each individual object.
In this example, both meshes are receiving this material in which the ObjectRadius is fed into Diffuse. The ObjectRadius output is being divided by 512 to provide a more meaningful visual result.
Panner
The Panner expression outputs UV texture coordinates that can be used to create panning, or moving, textures.