Dark Faces in solid viewport (pics)

Hi guys!

Pretty new to Blender, but I’m tryying to model a human head, but as I’m almost done with the head some of the faces are in a different color and aren’t smoothing as the other faces when in viewport solid mode. Anyone got an idea to why this is?

Ensure your face normals are consistent
Select all vertices and remove doubles (W / remove doubles), then recalculate normals (Ctrl+N)
To flip selected faces use W / Flip normals

For other problems select one of the faces and move it so you can see if you have any crap modelling and extra faces where you shouldn’t have faces