Hesperornis, as a diving bird, is often pictured as being underwater. Not much of that art has captured the scene as perfectly as this illustration I fear. The coloration of Hesperornis I will look into, I cannot say anything about the coloring in these illustrations today as I know basically nothing of it to begin with, but that aside the body form and the bird's carriage of itself both in and out of the water is fantastic. The legs of Hesperornis were what gave it power and as such were oriented near the rear of the animal yet still held somewhat under the belly and chest as the animal is believed to have, on land, carried itself in a slight forward bend, not unlike a Loon. This, unlike penguins, makes running difficult with the situation of the legs and hips at the very nearly extreme end of the rear of the animal; as far as center of balance is concerned I should say, not the actual skeletal rear of the animal. However, this being a foot propelled diving bird, Hesperornis' legs were adapted to maximize the strength and mechanical effort of these legs. The feet, as can be noticed here, are not webbed either, meaning some of the power was lost to the dive and swimming. These feet are comparable to the modern model that has been mentioned previously, the Grebe. Webbing would have made a much more efficient thrusting motion, but as it is not thought to be a part of Hesperornis anatomy, it is assumed that the dive of Hesperornis was powerful, but not as powerful as it could have been.
Older images of Hesperornis assume that webbing between the toes and, as far as I have seen this is an assumption as much as not having webbing is, but remember it is Saturday and I do my research one day at a time, just we all read it here! These illustrated Hesperornis also have the penguin body mentioned before. One thing they have which is a little more in what I have found to be the modern scientific thought, is that the leg is in the body wall down to the ankle. In the previous illustration it is not, but it is held at the same angle that the "in the body wall" theory states the feet would be held at, which, to me, makes it just a different interpretation of the theory. Here they align with the theory, but are held penguin-like, not Loon or Grebe like.
Old enough I can't find the artist
Other old illustrations, though science has flipped and flopped many times since they were engraved, I think that's an engraving, show an almost compromising juxtaposition between the old and the new. This one, for instance, has the newer designed feet with the older designed leg, i.e. not encased in the body wall, yet it shows Hesperornis as a belly-dragger on land. One school of thought is that the feet were placed so strangely on the body that this type of locomotion would have been nearly, if not the only, efficient method of locomotion for Hesperornis species to engage in when out of their marine environment. This makes them sound and look a lot like plesiosaurs, to be honest, which is not what we want to think about when we think about birds, but it is just possible that this locomotion would have been the most efficient type of terrestrial locomotion for this bird.