Glom
Here are some links
http://www.ntsb.gov/ntsb/query.asp
http://amelia.db.erau.edu/gen/am.htm
The first link is The US accident database.
The second link is to Embry Riddle University library.
In the US the FAA and I believe its Predecessor The CAA(USA) have operated a waiver system for colour defective pilots.
It has been called different things over the years
first it was called a waiver, and then later called a Statement of Demonstrated ability, SODA.
about two years ago they removed the requirement for a waiver altogether.
Basically what it all boils down to is if you can pass the signal light gun test at an airfield they will issue you with a letter of evidence, this is good for all subsequent medicals of any class for life.
Current estimates put the number of colour defective pilots with FAA medicals in the region of 10000.
Slightly less than 1/3 of the total number of pilots licensed by the UK CAA
If you Search the accident database in the link above
use the Following settings, Set the date in the first field to 1/1/62
This is the earliest record in the data base.
Don't Forget that Our american cousins spell Colour, Color if you know what I mean.
What you will Find if you search the Database for color vision is about 8 or so accidents stretching back to 1962.
None of the accident reports cite defective color vision as a cause or factor in the accident.
The reason that the search throws up these reports is invaribly that in the medial notes it was recorded that the pilot had a waiver or SODA for color vision.
The other link contains all the aeromedical research reports conducted by the FAA. You will find a lot of useful info here although it is a bit of a trawl to get through it.
Regards
DOH