Number of small cubes having one face green and the other one is either red or black = 8 x 2 = 16

Number of small cubes having no face coloured = (x - 2)³

= (4 - 2)³

= 8

Number of small cubes having three faces coloured = 1 at each corner

= 1 x 8

= 8

Number of small cubes having only one face coloured = 4 from each face

= 4 x 6

= 24

Number of small cubes having two faces coloured = 8 + 8 + 4 + 4 = 24

and Number of small cubes having only one face coloured = 4 x 6 = 24

and Number of small cubes having no face coloured = 4 + 4 = 8

Therefore, total number of small cubes whose at the most two faces are coloured = 24 + 24 + 8 = 56.