Common flatbed scanners typically register values from about 0.0 to 2.4. Although image density ranges from pure white to pure black, no detail can be seen in those areas. As you progress from pure white into slightly darker areas, detail emerges. The same is true at the other end of the spectrum. The dynamic range is calculated by subtracting DMin from DMax.
Color depth refers to how many bits are assigned to each pixel in an image.
When these files are processed down to 24-bit files, they contain images with more subtle gradations of color and more color accuracy. The quality of the colors in a scanned image depend not just on depth but on their registration . Since the colors are being captured by different sensors or at slightly different times, they may not overlap perfectly. If they don't color fringes will appear around details in the image. When scanners were first connected to PCs, that's pretty much the way it was.