The dodecahedron can be made, as usual, in only one color. However, it is more striking to build all of your models with parallel faces being of the same color. The Dodecahedron will need 6 colors. You must cut two pentagons of each color.
Assemble each of five color faces around the remaining color pentagon. This might look like a flower with a central piece and four petals. This is now one-half of your polyhedron. Do not combine the other 6 pieces into a similar one-half dodecahedron. You should be able to see where to apply the next color face (use a color from one of the petals) because it will be exactly opposite and parallel to the face with its same color.
Again, the last piece should be applied with one edge connected like the hinge of the top to a box. Once that edge is dry, the remaining 4 edges should be glued at the same time and then lowered and held in place until the glue dries.
To see the full-sized template click on this image: