Subsurface scattering field I have color A and color B and you want sub surface scattering.  My question is, on the "thickness" map, does pure white represent complete translucency or does grey?

White would mean I'm taking 100% of color B right?  Which means color A will not be present at all which isn't translucent.  So my guess is .50 (grey) is the true value if you want both colors?  Or am I wrong?

I already tried this with principle shader with red and blue creating purple with .5 (grey) sub surface scattering:



If I have white, I would be taking 100% of color B, thus there is no translucency with the red.

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So my basic question is, when I make a sub surface scattering map, should I be using grey for max translucency?  Or is there something I'm missing here?  Because I have seen White areas in thickness maps before which makes no sense to me, you're just taking 100% of color B?
When Subsurface is 1, the Base color has no influence.
Still you can use  radius to extract different colors from the Subsurface color.

Why it doesn't work for you
You're using RGB Blue (0,0,1), so Red and Green cannot be extracted (as they're zero).

Example
I'm using some random Blue containing all three channels (RGB: 0.14, 0.19, 0.8):


Subsurface = 1 (so the base color has zero influence)
I can bring up plenty of Red from my Blue, using the Subsurface Radius.