Singapore Work permit - Colour blindness issue

Hi Sir,

For my friend, a couple of days ago, an employment agency tried to submit an IPA application for work permit, however, whilst trying to apply they can't even enter his particulars online and got the following error message:

"The foreigner is not eligible for a work pass because he/she is medically unfit". Please advise your employer to look out for another candidate."

Kindly be advised that my friend (the worker) has colour blindness problem.

I have the following questions to you looking for your valuable advice:

1. Would be be able to work again in Singapore if he has colour blindness? If yes, what could be the possible ways to get it done.

2. He worked previously as electrician. So, he wasn't able to continue his employment being an electrician with colour blindness. Can he work under different occupation other than that?

3. Any history of employees who were able to secure the job after they diagnosed with colour blindness?

4. Do MOM hold any sort of registry for the unfit/ blacklisted employees? Is there any sort of waiting or hold up period?

My apologies for listing so many questions. Awaiting your valuable response, thanks very much in advance!