Diplodocus is one of the longest animals in the land and it feeds on ferns, club mosses, and other plants. Since diplodocus is an herbivorous, it mostly feeds on plants. To start with, it will be great to paint the entire background with green color to represent the color of plants which diplodocus feeds on. As you can see from the sketch diagram, this animal has a long neck and four sturdy legs. Diplodocus is a reptile and it will be in order to color it similarly like other reptiles. You can use grey color to paint the diplodocus body to give it a vivid texture. There are some scales on the upper part of the body. These can be painted with black color. Since this is a large diplodocus, it is important to color it more conservatively. When you use grey color on the entire body of this animal, it will definitely match with their surroundings for the purposes of protection. The long neck of diplodocus enables it to venture into large forests. The teeth can be painted with white color to depict how long they are for the purposes of feeding on large herbs as well as other plants. There are some stones on the way and these can be painted using brown color to give a picture of the kind of terrain where this animal walks through when hunting for food. You can also paint the clouds with light grey color to show the kind of environment where this animal dwells in.