I am currently studying the textbook Modern Optical Engineering, fourth edition, by Warren Smith. Chapter 1 presents the following diagram and explanation when discussion interference and diffraction:
If the illuminating source is monochromatic, i.e., emits but a single wavelength of light, the result will be a series of alternating light and dark bands of gradually changing intensity on the screen (assuming that $s$, $A$, and $B$ are slits), and by careful measurement of the geometry of the slits and the separation of the bands, the wavelength of the radiation may be computed. (The distance $AB$ should be less than a millimeter and the distance from the slits to the screen should be to the order of a meter to conduct this experiment.)
The author then goes on to say the following:
Now if the light source, instead of being monochromatic, is white and consists of all wavelengths, it can be seen that each wavelength will produce its own array of light and dark bands of its own particular spacing. Under these conditions the center of the screen will be illuminated by all wavelengths and will be white. As we proceed from the center, the first effect perceptible to the eye will be the dark band for blue light which will occur at a point where the other wavelengths are still illuminating the screen. Similarly, the dark band for red light will occur where blue and other wavelengths are illuminating the screen. Thus a series of colored bands is produced, starting with white on the axis and progressing through red, blue, green, orange, red, violet, green, and violet, as the path difference increases. Further from the axis, however, the various light and dark bands from all the visible wavelengths become so “scrambled” that the band structures blend together and disappear.
I'm wondering why the coloured bands appear in the specific order of red, blue, green, orange, red, violet, green, and violet. It seems that it has something to do with wavelength, but I'm not sure. I would greatly appreciate it if people would please take the time to explain this.