This allows all iemguis except
[vu] to inherit their color from the GUI preset if the color is the default.
E.g., if the foreground color for a
[bng] is "#000000" then it will be changed to whatever the foreground color happens to be for the given GUI preset. On the default preset this is just "#000000" so there's no change. But on inverted presets and others this color choice will get changed to the preset's default color.
This way, Pd Vanilla patches with default iemgui colors will work by default with the GUI presets.
One esoteric detail-- the default iemgui background color is "#fcfcfc" instead of pure white.
In the (unlikely) case that someone has designed an interface to use specifically with a given GUI preset, they can change from "#000000" to "#1 (closed) or something like that.