In this version, I attempt to present a range of colors within tolerance of the federal specifications for each defined color. You will need to use some kind of color-picker tool to extract color values from the swatch images provided. As each swatch represents a range of colors, mixing colors from the same swatch should result in colors which are within tolerance for that defined color.
Source: Federal Highway Administration 23 CFR Part 655 as defined in Federal Register Vol. 67, No. 147, and amended in Federal Register Vol. 67, No. 225. Except black, which not covered by the federal specs; however, even the darkest common materials reflect some light, so I've thrown in a selection of very dark colors. Reflectance values are as specified for Types IV, VII, and VIII sheeting where applicable. Brightness is calibrated so “pure white” on the screen represents 71% reflectance (fairly high); the background of this page is a neutral gray at 50% reflectance. Most of these colors cannot be represented at their full saturation in the sRGB color space. Irregular swatch edges indicate where the color may continue to vary within tolerance, but such color is too intense to represent in sRGB. Future versions of this document may include nighttime colors as well.
This document is copyright ©2008–15 Vid the Kid (me) and presents the results of calculations performed by myself and software I wrote. My understanding of color spaces and the math involved was improved largely by articles on Wikipedia and the website of Bruce Lindbloom. Thanks.