have you tried toggle.setColorFilter(0xAARRGGBB, Mode.SRC_ATOP); ?
you'd need to find the correct #AARRGGBB code for a greyish color, but it should work.
EDIT: Ok, so after playing around with the settings a bit I found that this works pretty nicely for greying something out toggle.setColorFilter(0xA6A6A6A6, Mode.SRC_ATOP);
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