Colour is very significant to Breaking Bad, with Gilligan often using it as a way of symbolism. And, you will notice that colour is especially important when discussing the characters' clothes.
At the beginning, Walt was dressed in a lot of white and beige, showing his mild-mannered and boring personality. And, although he is still dressed in this colour throughout, it is a decidedly darker shade of the colour by the end, showing his evolution to the dark side.
This is also very true of the evolution of how Skyler is dressed throughout, as she becomes more involved in Walt’s life of crime.