Subsurface color versus scattering color in SSS material?

[SonyBoy]

Can anyone give me an idiot's guide explanation as to the difference between the subsurface color and scattering color attributes on the fast SSS material? I've never quite grasped this and unfortunately the docs aren't much help, with the example images for these two attrs. looking more or less the same. In addition in most cases you want to use the SSS attributes in order to create the illusion of scattering of the shader's diffuse color (e.g., a red candle), rather than complete color changes like in the examples given. Presumably there is a methodology intended in the uses of these two parameters, but I've never seen a clear explanation of it. So, this usually ends up being a pretty time consuming case of trial and error, with mixed results. Thanks!

[SonyBoy]

Just noticed the docs for Next are a little more helpful than those for 3.6. However, still presented in a pretty confusing way. "Note how changing the Sub-surface color changes the overall appearance of the material". OK, but then how does this relate to both the diffuse and overall color, which in conjunction with scattering presumably could achieve a similar result? How does the Subsurface Color contribute to the SSS effect? Is it even necessary to use this attribute in some cases?

[yolov]

Will it help if we put a note on what the math behind it is? (what gets multiplied by what and added to what)

[SonyBoy]

It might help someone more technically minded than me -- I'm really just trying to grasp what the practical difference is between those two parameters and how to use them without as much trial and error.

[yolov]

I'll make a note to add some more user-friendly descriptions.

[SonyBoy]

Also, a few more presets would be great for a few more common material types, e.g. wax. I've always thought the existing presets were an odd bunch of choices, with two types of milk, and ketchup! :P