There are several ways to do this,Using a mod. It's possible. Maybe cube could find our a way around this?View attachment 133579
1. Using mcpatcher & adding a damge value / metadata to a dragon egg, This way you can change textures for individual teams (Mcpatcher comes with OptiFine, might not be possible for pre-1.11 versions)
2. Using 3dmodels to change a normal block into a dragon egg of each color (This way you'd lose a few building blocks, would work for 1.8+)
Both would require a server resource pack, there might be other ways to do this, this is what I could think of for the moment