Color vision testing for employers

Updated November 2026

About 1 in 12 men has a color vision deficiency, and the most common type makes it hard to tell red from green (National Eye Institute). Many people with a mild deficiency never notice it until a job depends on color. If color carries meaning in your work, for example wire colors, warning lights or stained lab samples, a short screening helps you find out early who needs a closer look.

This guide explains which roles usually need color vision screening, when you can screen candidates in the U.S., how to run the screening and what to do with the result.

This page is general information, not legal or medical advice. A screening does not diagnose a color vision deficiency. Only an eye care professional can do that.

Which jobs need color vision screening?

Color vision matters wherever color carries information that affects safety or quality. Common examples:

Electricians and technicians. Insulation colors identify neutral and grounding conductors. See our guide Color vision test for electricians.
Commercial drivers. U.S. DOT rules require the ability to recognize the colors of traffic signals and devices showing standard red, green and amber. See DOT color vision requirements.
Laboratory and healthcare staff. Test strips, stained samples, color-coded tubes and alarms.
Manufacturing and quality control. Color-coded wiring harnesses, paint, textiles, displays and packaging.
Rail, aviation ground crews and control rooms. Signals and alarms are often color-coded, and some of these roles have their own rules that require an exam by a physician or a specific test.

Before you add a screening, write down why the role needs it and which colors matter. A clear, job-related reason makes your process fairer and easier to explain.

When can you screen candidates? (U.S.)

Under the Americans with Disabilities Act, the EEOC treats a vision test, such as reading an eye chart, as a medical examination. Its guidance says:

An employer may not conduct medical examinations until after it makes a conditional job offer.
After the offer, all entering employees in the same job category must go through the same examination.
Medical information must be kept on separate forms and in separate medical files, not in the regular personnel file.

In practice: screen after the conditional offer, screen everyone in the same job category the same way, and keep the results with occupational health, not with the hiring manager. Rules differ between countries and states, so check your process with your counsel.

How to run the screening

Most employers use one of three options:

A paper Ishihara plate book in an occupational health office. Well known, but it needs an in-person visit, good lighting and plates in good condition, and the record usually stays on paper.
Referral to a clinic. Simple for you, but every candidate costs a visit, time and a fee.
Online screening. The candidate opens a link on their own phone or computer and completes the screening in a few minutes. You get a result and a record without a visit. Screens and lighting differ, so an unclear or failed result should always lead to a follow-up exam.

Whichever option you choose, use the same method for everyone in the same job category, and record when the screening was done, which test was used and who reviewed the result.

What to do when a candidate does not pass

Do not treat a screening result as a diagnosis. Refer the candidate to an eye care professional for a full color vision exam.
Check whether the job really requires the color task, and which colors. Many people with a mild deficiency can still recognize the specific colors a job uses.
Where it fits, look at the actual task, for example identifying the wire colors or signal colors used on the job.
Keep the result, the follow-up and your decision in the confidential medical file, and talk to your counsel before you withdraw an offer.

Frequently asked questions

Is the free test on this website enough for hiring decisions?

No. The free test is for personal information and education. It does not create a record for your files and it does not diagnose. For candidates, use a documented process and refer anyone with an unclear result to an eye care professional.

Can we test candidates before making a job offer?

In the U.S., EEOC guidance says medical examinations, which include vision tests, are only allowed after a conditional job offer. Rules in other countries differ.

Which test is used to screen for red-green color vision deficiency?

Plate tests based on the Ishihara principle are the most common screening for red-green deficiency. Eye care professionals use further tests to find out the type and degree.

How often should we screen?

Most employers screen once, after the offer, because inherited color vision deficiency usually does not change. Some sectors require repeat checks at set intervals, so follow the rules that apply to your industry.