On this page you will find chroma charts for various services such as the railroads, aviation, marine, etc.  The first chart gives you an idea of the colors, where they are on the chart, what their wavelength is in relation to the color, and the fact that as we go in towards the center, things get progressively whiter.  Most of the charts are self labeled as to the industry they cover.

Notice that around the outside we have the wavelength shown, except for between purple on the bottom left, and red on the bottom red..... that's because those colors do not correspond to a natural wavelength - and you won't find those colors in a rainbow or the bands of light made from a prism splitting white into its component colors.

Above, AAR chroma chart for the railroad industry.

NEW 15MAR2009, 1SEP2013, 11SEP2018
Last Modified  05-Sep-2019