As Anthanasius says, the shader has a reflection node which will give you the variation from pure white that you want. Your lighting will also affect the apparent colour of the snow. I also find that ambient occlusion in the IBL light gives a nice tonal quality to the snow. I usually set it to 10 inches or more. Please note that one of the check boxes on the user interface is 'Do it quicker', which switches off the reflection node. This is intended for preview rendering while developing your scene. The final render should have that box unchecked in order to activate the reflection node. On the other hand, I have plans to include a colour picker in a future release so that it can be used for things like cake icing etc. In the meantime, lighting, ambient occlusion and reflection will achieve what you want, I think.

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