A free program for Android, by Redail Software.

3D Revit Manual For PC is a free app that will allow you to make a model or building in the popular 3D modeling software Revit—no need to learn software or modeling skills. Select the object type, location, and size, then start creating. The app will allow you to make a building, a house, a tree, a wall, a floor, and other objects, all of which can be modified to your liking. Once your model is finished, you can import it into Revit and edit it.

You will be able to change the color and the texture of the objects, the walls, the floors, and the roof. You can also change the height of the walls and the roof.