Tail and stop lights need to be red and no clear covers. Some state allow amber on turn signal colors but rear tail lights have to be red and clear covers are also forbidden. I looked mostly for amber turn signals but federal law 108 is pretty clear on color and intensity of all the turn, marker and head lights of all vehicles. I have heard of some being ticketed for amber rear turn signal lights. But when it comes standard on some cars I dont see how they can say you cant have amber. I too was interested in this and never looked into it so I spent a couple of minutes and looking and this is what I found.
Until the early 1960s, most front turn signals worldwide emitted white light and most rear turn signals emitted red. The auto industry in the USA voluntarily adopted amber front-turn signals for most vehicles beginning in the 1963 model year, though the advent of amber signals was accompanied by legal stumbles in some states and front turn signals were still legally permitted to emit white light until FMVSS 108 took effect for the 1968 model year, whereupon amber became the only permissible front turn signal colour. Presently, almost all countries outside of the United States and Canada require that all front, side and rear turn signals produce amber light.
In Canada and the US the rear signals may be amber or red. American regulators and other proponents of red rear turn signals have historically asserted there is no proven safety benefit to amber signals, though it has been recognized since the 1960s that amber turn signals are more quickly spotted than red ones. International proponents of amber rear signals say they are more easily discernible as turn signals,[59] and U.S. studies in the early 1990s demonstrated improvements in the speed and accuracy of following drivers' reaction to stop lamps when the turn signals were amber rather than red.
In 2008, NHTSA (the U.S. National Highway Traffic Safety Administration, responsible for writing U.S. vehicle safety standards) released tentative findings that amber (“yellow”) turn signals are up to 28% more effective at avoiding crashes than red ones. Then, in 2009, they released preliminary findings that across all situations, including those in which turn signals don’t matter, vehicles with amber rear turn signals are 5.3% less likely to be hit from behind than otherwise-identical vehicles with red ones.
There is some evidence that turn signals with colourless clear lenses and amber bulbs may be less conspicuous in bright sunlight than those with amber lenses and colourless bulbs.
Amber rear signals are required in Europe, Australia, New Zealand, all of Asia (including Japan, China, and Korea), South Africa, most of South America, and virtually the entire rest of the world. Outside North America, red turn signals have been banned almost everywhere for 35 to 55 years.
Are clear tail lamp lenses permitted?
No. Washington has adopted the Federal Motor Vehicle Safety Standard (FMVSS) 108 for all aftermarket lighting equipment. FMVSS 108 is very specific for tail/brake light lenses as well as front side marker light lenses. Most clear aftermarket lighting lack the required reflex reflectors and side marker lights. Using "red" bulbs in clear lenses is not acceptable as it does not meet FMVSS 108. All aftermarket lighting must have the same functionality as those originally installed.
The National Highway Traffic Safety Administration is asking for public comment on a proposed new regulation that would mandate vehicle rear turn signals to be amber-colored. Currently, they can be either amber or red, in accordance with Federal Motor Vehicle Safety Standard No. 108.
So there you have it Federal Motor Vehicle Safety Standard No. 108. says either red or amber but no colored bulbs or bulb covers. States cannot supersede this standard and if given a ticket can hold up this law. In case you want to look into this yourself I have included some links to start with
http://www.wsp.wa.gov/traveler/pasfaqs.htmhttp://en.wikipedia.org/wiki/Automotive_lightinghttp://www.fmcsa.dot.gov/regulations/title49/section/393.11https://www.federalregister.gov/articles/2011/08/08/2011-19595/federal-motor-vehicle-safety-standards-lamps-reflective-devices-and-associated-equipment
