Is it permissible to accept a deferred commission from a colleague in return for following up with the company, or is it considered a charity that is impermissible to accept?

If the insurance is cooperative (تكافلي), then there is no objection to working in it or accepting commissions from a colleague. If money comes without being requested, the person may take it. However, if the insurance is commercial, based on gharar (uncertainty) and gambling, then brokering in it is not permissible, and earnings from it are illicit and must be disposed of by spending them on the welfare of Muslims and the poor. It is not permissible to benefit from it except for the poor and needy, to the extent of their need. Commissions from a colleague must be taken from the company and spent as mentioned.