I think we don't even need to consider permission in order to resolve this question. The more fundamental question is this: how do you know that "personal communication" is the right citation and not a publication?
Your colleague may have been passing on information that they or somebody else had already published. Even if it was not published when the colleague spoke to you, it may have been published (or at least submitted) as part of some manuscript since. It may also have been communicated to you in confidence---you would hopefully remember if this was the case, but in some cases it may be easy to forget, e.g., if it was said during a UK meeting held under Chatham House Rule or at a Gordon Conference.
I would thus recommend contacting the colleague to ask what the appropriate citation for the information is. At that point, the colleague can make an appropriate judgement and either point you to a standard citation, tell you to cite as personal communication, or request that you not publish the information.