I thought I'll add my 2 cents in as well.
You should look at colours that are generally associated with your field. For example people normally associate the colour
red with words like
important,
danger,
stop. Whereas the colour
green is usually associated with the
environment,
go,
safety etc. As an extreme example today homosexual community, they have adopted the rainbow colours.
Society around us have certain established norms, practises etc. It is very hard to go against these established norms. Some times going against them can make people uncomfortable. It confuses them. You'll have to be a very good designer to be able to ignore these.
The colours I personally would associate with motor vehicles are:
- Orange; RAC, combs used to block roads.
- Yellow; AA, florescent jackets.
- Red; Road signs, although only a little.
- Silver; Metallic body parts.
Personally I would advise having at least 3 colours, two complimentary colours and one that just stands out and shouts at you. e.g. blue and silver and then either a little maroon/brown/purple/yellow/orange.