X-ray fluorescence spectroscopy (XRF) is a powerful tool that reveals the hidden colors of chemical elements, changing our understanding of Nature. This technology is widely used in various fields, including industrial quality control, environmental analysis, and art conservation. A new advancement in XRF is x-ray color imaging, which captures images of chemical elements in the x-ray wavelength range. There are two techniques: scanning and projection. Projection-type x-ray color imaging is a breakthrough development that uses 2D semiconductor detectors, allowing real-time imaging and dynamic tracking of chemical reactions. This innovation has the potential to transform several scientific fields, allowing scientists to study complex systems and reactions in ways never before possible. This book explores the technology and applications of this new imaging technique. Part of IOP Series in Sensors and Sensor Systems.