This is how I would do it:
dtype = np.dtype((np.void, (p_a_colors.shape[1] *
p_a_colors.dtype.itemsize)))
mask = np.in1d(p_a_colors.view(dtype), p_rem.view(dtype))
p_r_colors = p_a_colors[~mask]
>>> p_r_colors
array([[0, 0, 0],
[0, 2, 0],
[3, 2, 4]])
You need to do the void dtype thing so that numpy compares rows as a whole. After that using the built-in set routines seems like the obvious way to go.