Mottle \Mot"tle\, v. t. [imp. & p. p. {Mottled}; p. pr. & vb. n. {Mottling}.] [From {Mottled}.] To mark with spots of different color, or shades of color, as if stained; to spot; to maculate.
mottling n : the act of coloring with areas of different shades