def g(r,g,b,r2,g2,b2,s){ (0..(1.0/s)).collect { c -> [(int)(r*s*c+r2*(1-s*c)),(int)(g*s*c+g2*(1-s*c)),(int)(b*s*c+b2*(1-s*c))] } } g(0,0,0,255,255,255,0.1)