Effectively, for most people, there is no real difference. Some people prefer one form, some the other.
Some people feel that there is a difference in meaning. They feel that it is the getting of the promotion that is being resented in #1; such people usually use 'of' after 'getting', considering it to be a 'verbal noun'. They feel that it is the colleague who is being resnted in #2 (for getting the promotion); they do not use 'of' after 'getting', considering it to be a gerund (verbal noun).
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