In the movie of Jurassic Park and in the museums of natural history, most of the classic dinosaurs have featherless, dark-colored, lizard-like skins.
Recent studies of fossil records show that a real dinosaur may look far better than that. In a 2010 Science paper, paleontologists reconstructed a small, feathered, bird-like Jurassic (~160 mya) dinosaur, Anchiornis huxleyi. In general, colors of extinct organisms are very rarely preserved in the fossil record, and thus it is difficult to re-establish the color of an extinct species. Melanosomes are organelles held in soft-tissue structures such as skin and feathers, which contain the pigment melanin. Quantitative comparison of melanosome shape and density between fossil records and modern black, grey and brown feathers helped to determine the color patterns of the skin and feathers of A. huxleyi. The re-constructed A. huxleyi reminds me the special bird I saw in San Diego Zoo, Cassowary. Cassowary, the third largest and most dangerous living bird, probably the closest creature to a living dinosaur.
In a 2011 Science paper, well preserved dinosaur feathers were found in late Cretaceous (~80 mya) ambers from western Canada. Those feathers display a wide range of pigmentation, ranging from nearly transparent to dark. However, the researchers did not think this discovery could lead to a Jurassic Park scenario since those specimens are extremely small and would not be expected to contain any DNA material.
Ref: (1) Li, Q.; et al. Science 2010, 327, 1369.
(2) McKellar, R. C.; et al. Science 2011, 333, 1619.