In k-out-of-n visual cryptography scheme  the secret image is encoded into n shares and each share is printed on a transparency. Then the secret image can be obtained only by stacking k of the n shares, but we cannot get any information about the secret image from fewer than k shares. A colored VCS, in which the secret image is comprised of colored pixels, has been studied by some people, but known constructions lose a lot of contrast in reconstructed images. In this paper, we introduce a new colored VCS, which uses only four colors, black, white, red and green, and propose its construction with high contrast by using the property that a stacking of a red subpixel and a green subpixel results a black subpixel. We provide a construction of such a 4-colored  with contrast  for  and prove that these contrasts are sharp. Moreover, we show that the pixel expansion of our construction is also sharp.