How to effectively recover the money borrowed by colleagues?

It's really embarrassing and uncomfortable to encounter this situation. Here are some suggestions:

1. Let the other party realize the fact of the arrears: you can write an email or send a text message to the borrower to remind him/her how long he/she has owed money.

2. Propose reasonable solutions: You can propose some reasonable solutions, such as installment repayment or extending repayment time.

3. Make a clear repayment plan: You can discuss with the other party and make a clear repayment plan to let the other party know the specific repayment time and amount.

4. Seek the intervention of a third party: If the above methods fail to solve the problem, you may need to consider seeking legal help or taking arbitration procedures to recover debts.

No matter which way you want to take, you should remain calm and polite, and try to be reasonable and respect each other's opinions.