Hello Sebbin Joshy. Thanks for contacting Careers360 and we hope we will be able to answer your query. 

No, there is no such dress code to be followed for JEE Mains. I would advice you to just wear casuals, that is, shirt and pants / jeans. 

First, please start preparing seriously instead of worrying about such trivial matters. Please review the concepts thoroughly and practice at least two or three past year or mock papers.

Hope this helps you and all the best!