Current progress in the exciting and burgeoning field of functional defects in colloidal photonic crystals (CPCs) is reported. After a brief introduction into the importance and nature of defects in CPCs the state-of-the-art in fabricating point, line, and planar defects is described. Measurement and characterization techniques as well as the corresponding theory are discussed. Besides normal, passive defects, the recent development of reversibly tunable defects adds important functionality. In particular, the addition of chemical functionality is demonstrated to open a path to a wide range of color readout devices for ultrasensitive optical detection of biomolecules and pharmaceuticals.