Why are the mesh faces different colors? In the 3D View window the mesh I am modeling appears with two different colors.  The final render has one color.  

it's my first day learning blender and I'm following a tutorial to create a house model. In the tutorial the different faces of the house are all the same color, but my faces are having two different colors. I'm wondering why was there a color applied and what does it mean? When I render the model it's all the same color.
While I can't tell you why they're in this state currently, as there are many possible reasons, these colors indicated the direction in which the face normals point. To fix this, you need to recalculate your faces' normals, by pressing Ctrl + N. Alternatively, this can be done from the toolbar (whose visibility is toggled by pressing T),by pressing Recalculate found in the Shading/UVs tab of said toolbar.