Who should be tested for color vision deficiency?

Security, drivers. Good color vision is vital for recognizing various lights and signals important to pilots, especially at night. These tests are required by, among others, the coast-guard and most military and emergency services. Unfortunately, if you really are colorblind, there is very little you can do to pass these tests.
Occupational needs. Color deficiency causes a change in the perceived spectrum of objects that are colored. There are some occupations which require normal color vision including law enforcement, pilots, ship captains, fruit graders, color mixers and electronic device assemblers. You might need to be tested for normality for one of those occupations.