X-ray images are traditionally in black and white, they work by sending X-rays through a patient and looking for the shadows cast by bones and tissues. Even the more modern 3D CAT (Computer Aided Tomography) scans work by combining many conventional x-rays into a 3D image, (find out more about X-rays here.)
However X-rays are a form of light so they can have many different wavelengths in the same way that visible light has many different wavelengths which we call colours. Our eyes gather lots of useful information about the world from the colours of light that an object reflects, so doctors should be able to do the same with the wavelength or colour of the X-rays a tissue affects.
Now Robert Cernik in Manchester has built a 3D scanner that sends a mixture of wavelengths of X-rays into an object and then looks at the X-rays that bounce off the material inside the object. By moving the detector and the beam you can build up a 3D X-ray colour picture of the object.
Different tissues have different amounts of metals which interact strongly with X-rays, so the hope is that this technique will allow doctors to identify damaged tissue deep within the body without having to open you up.
However it is stil very much early days, because the sensors are not very effective at the moment it takes 3 hours to image a 5x5mm area and the radiation dose leaves it heavily damaged. However Cernik is going to try use a more sensitive form of detector that should speed the process by a factor of 100.