A clever way to convert monotone video to a color one

I is a monotone video with dimension [width, height, length];

V = permute(I, [1,2,4,3] );%size(V)=[width,height,1,length];
V = repmat( V, [1,1,3,1] );%size(V)=[width,height,3,length];

V is a 3-channel video (every channel is the same), though.