Yes! By colleagues we assume both former and current workers. We try with three things:
1. Allowing coworkers to write anonymous private message to the user.
2. Asking user feedback though rating system on their technical skills. Rate users as beginner, intermediate, expert and advanced.
3. 4 simple questionnaires with 7 multiple choice questions in each to get reviewed on their qualities. These questionnaires review users on their professionalism, collaboration, leadership and interpersonal skills.
The collected data from Point 2 and 3 above is then aggregated based on the colleague relationship (current has more weightage then former coworkers) and presented to the user in an easy to understand graphical format which basically identifies their strengths and weaknesses. In the whole, user identity who rated is not revealed in any step, we just tell user that he has been rated by one his coworkers in one of the companies he has worked and listed on his profile.
On top of that on each quality and skills, we have assembled list of articles curated from top sources so that user can improve these skills. He can also subscribe to other skills he is interested in learning and they are made available to him in his personalized feed.
Hope that helps!