Yes there is some information in the Arnold user guide on how to create one.
Except those are for one shader with two different colors on each side.
A double sided shader is useful to create realistic leaves, and other thin objects.
This is one way to create a double sided shader for Arnold.
- Create two aiStandard shaders.
Name the first as front_shader and the second as back_shader.
- Create a samplerInfo node and a condition node.
- Connect the Flipped Normal (samplerInfo node) to First Term (condition node).
Set the Second Term to 1. Set Operation to Equal.
- Connect the front_shader’s Message to Color If False (condition node), back_shader’s Message to Color If True (condition node).
- Create a surfaceShader.
- Connect the condition node’s Out Color to the surfaceShader’s Out Color.
- Assign the surfaceShader to an object.