K... I just did a round of tests.

First, with the "math" node in place (the way I have it set up in image above), I spot rendered to find any seam problems, as well as spot rendered with the default face (no paint), no seams and no differences.  I pretty much decided that this is how I'm gonna do.  But I tried your suggestion as well.

After replacing the math node with the "Blender" node, left them both white (default), set the setting at 1.000, and spot rendered.  It does look good, but there is a slight difference in the way the light's reacting, just a tad... no seam problems that I saw though.  Changing the colors back and forth (black/white) made no difference.  What I'm thinking here, is that this is one light setting I'm rendering in, another light set may make more difference, don't know, so I'm just gonna stick with the "Math Function", it makes common sense to me that it's serving as a simple extra plug with strength settings & no color to play with.