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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _find_colour(particle, start_index, screen_data):
 """ Helper function to find an existing colour in the particle palette. """

        _, fg2, attr2, bg2 = screen_data
        index = start_index
        for i, colours in enumerate(particle.colours):
            if (fg2, attr2, bg2) == colours:
                index = i
                break
        return index