This chapter introduces modern mass spectrometry for the detection of dyes in foods. An LC/MS/MS method for the determination of 20 synthetic dyes is first described. Followed high resolution mass spectrometry (HRMS) demonstrates the modern screening method for illegal dye adulteration. There is an example of semitargeted/ non-targeted detection and structure confirmation of a non-permitted dye, diethyl yellow, by quadrupole-orbitrap HRMS. Mass spectrometry operated on selected reaction monitoring (SRM) is gold standard normally used for the detection of analytes such as pesticides, veterinary medicines and additives such as dyes in complex matrix. However, SRM only allows signals which fit target list to be recorded. It will lose all information of semi-target, non-target or even unknown. A new concept called dataindependent acquisition (DIA) overcomes the limitations of SRM and increases the possibility of semi-target and non-target detection. This chapter includes the application of DIA for simultaneously screening and confirmation of dyes in various foods.