Hello Mahi,
I am not sure what you mean by 'body language' in the given context.
Also, the focus/importance on the 'body language' [as it's understood generally] is NOT UNIFORM across all functions/sectors--for eg., a marketing person may need to have a lot more of 'proper body language' than one who is in, let's say, the Accounts function.
Also your usage of the words 'civil company' for describing your organization is a bit confusing--is it into Construction OR civil design OR Infrastructure, etc--hope you get what I mean, since there are a whole host of areas where Civil engg is the mainstay.
Regarding ensuring some sort of a dress code is followed, while a Formal Policy will definitely have to come to ensure uniformity in understanding & implementation, I am NOT SO SURE if starting the whole implementation with the Policy WILL WORK. Given the type of responses/reactions you seem to be facing, the policy could be counter-productive--UNTIL you handle the 'ego' part of the staff: HOW would be the key.
I can see 2 ways to handle this issue:
1] I am not sure of the sort of support you get from your CEO--apart from 'telling' you to educate the staff. If any policy has to be the Starting point, it has to come from the CEO & as HR, you need to implement it--that way, everyone will be clear about WHO is interested in this policy & also that you are just implementing it. The meeting that Pon & Archna suggested will then work very well to formulate the policy--since the chain-of-instruction is clear to all. The way I get it is this [hoping I am wrong]: your CEO is trying to fire from your shoulder--since, for whatever reasons, he doesn't want to use his/her own.
2] If the support you can expect from your CEO is, to say the least, very Minimal, then I suggest you DON'T TALK of any policies AT ALL to begin with. And also, NEVER EVER give the impression that you are EDUCATING them--first of all, you are new here & added to it, you realized only later about their 'ego' issues. I see a clear message in their 'anger': Who are you to teach/tell us NOW when we are living like this in this company without any remark from the CEO all these days/years?
The only way I can see you succeed [without your CEO's support/direct involvement] is to first endear yourself to them & only then raise the issues where you are not getting co-operation now, but would like to.
HOW? Frankly, I would leave this open to debate, since the right workable advice for this query could need many other inputs from your end depending on the thought(s)/suggestion(s) the members of this Forum may come up with.
Rgds,
TS