Canon T4i In-camera color not accurate?

Yes, calibrate your monitor. It makes a big difference in two ways:

• accuracy of colors (obviously)
  Helps if you want to change the white balance or "warmth" of your pictures to the correct value.
  
• tone curves (accuracy of blacks, shadows, midtones and highlights)
  This is less obvious but equally important. You simply cannot do good shadow and highlight recovery without getting this OK on your monitor. If your monitor is off then your pictures may look more noisy than they are and darker or lighter than they would be after print or when viewing them on the latest iPads.

Don't even bother with RAW without a properly calibrated monitor.