It looks like this could reasonably be considered to violate either the rule that the word must be in English ("colddd" is not in any dictionary of the English language) or the rule that your clue must be "only one word" without any additional hints.
That is: it's not "only one English word without any additional hints". With the extra information you're attempting to convey in the manner you say the word, you're either turning it into the non-English word "colddd", or you're adding additional hints to the word "cold".
But, as always, it's up to your group how much you want to hew to the rules, as per the "golden rule" of Codenames:
If the opposing spymaster allows it, the clue is valid. If you aren't sure, ask your opponent.