Capable of being colored or receiving color; also means plausible or seemingly reasonable even if not entirely truthful.
From Latin 'color' + '-able' (capable of being). The secondary meaning of 'seemingly true but deceptive' comes from the idea that color can make something look different from reality.
The second meaning is sneaky—a 'colorable excuse' isn't a good excuse, it just looks good on the surface, like painting over a problem instead of fixing it!
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