Blender is a free and open-source 3D creation suite. It supports the entirety of the 3D pipelinemodeling, rigging, animation, simulation, rendering, compositing and motion tracking, and even video editing and game creation.
One of the most basic things you can do in Blender is to change the color of an object. This can be done in a number of ways, but the most common is to use the Material Properties panel.