An institution should focus on the appropriateness of having a centralized review of suspicious transactions and recommendations to file an STR to ensure consistency. This is because a centralized review process can help to avoid duplication, inconsistency, or omission of STRs, as well as to ensure compliance with regulatory requirements and internal policies. A centralized review process can also facilitate the analysis of trends, patterns, and typologies of suspicious transactions across the institution, and enable the communication and coordination with relevant stakeholders, such as law enforcement, regulators, or other financial institutions.
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ACAMS Study Guide for the CAMS Certification Examination, 6th Edition, Chapter 5, Section 5.3.1, page
1911
ACAMS CAMS Certification Video Training Course, Module 5, Lesson 5.3, video time 2:30-4:002 ACAMS CAMS Certification Practice Exam, Question 124, page 2843

According to the risk-based approach, financial institutions should apply enhanced due diligence and ongoing monitoring to higher-risk clients, and take appropriate measures to mitigate the risks of money laundering and terrorist financing. If the client exceeds the criteria of an acceptable risk model created by the institution, the institution shouldcommunicate the issues to the client and request remedial actions, such as providing additional information, documentation, or evidence of compliance. If the client does not cooperate or comply with the institution's requirements, the institution should consider terminating the relationship with the client, as the risk may outweigh the benefits of continuing the business relationship.
ACAMS CAMS Certification Package - 6th Edition, Chapter 2: Risk Assessments, pp. 51-521 ACAMS CAMS Certification Package - 6th Edition, Chapter 4: Customer Due Diligence, pp. 97-981 ACAMS CAMS Certification Video Training Course, Module 2: Risk Assessments, Lesson 2.3: Risk-Based Approach2 ACAMS CAMS Certification Video Training Course, Module 4: Customer Due Diligence, Lesson 4.3:
Enhanced Due Diligence
Reference:
http://www.fatf-gafi.org/media/fatf/documents/reports/Risk-Based-Approach-Banking-Sector.pdf

According to the guidance issued by FinCEN and the Federal banking agencies, when a financial institution receives a request for SAR supporting documentation from FinCEN or an appropriate law enforcement or supervisory agency, it must first verify that the requestor is, in fact, a representative of such an agency. This is to ensure the confidentiality and security of the SAR information and to prevent unauthorized disclosures. A financial institution should have procedures for such verification in its BSA/AML compliance program, which may include, for example, independent employment verification with the requestor's field office or face-to-face review of the requestor's credentials.
References:
1: This web page explains the BSA requirement that financial institutions provide SAR supporting documentation in response to requests by FinCEN and appropriate law enforcement or supervisory agencies, and the need to verify the requestor's identity.
2: This document provides answers to frequently asked questions regarding SARs and other AML considerations, including the question of how to handle "keep open" requests from law enforcement.

According to the Anti-Money Laundering Specialist (the 6th edition) resources, the employee should report the conversation to the compliance officer because the colleague is engaging in tipping off, which is a serious violation of anti-money laundering laws and regulations. Tipping off is the act of informing a person or entity that they are the subject of a suspicious transaction report or an investigation, or providing any information that may compromise or impede the investigation. Tipping off can result in criminal penalties, civil liabilities, and disciplinary actions for the individual and the institution. Therefore, the employee has a duty to report the colleague's misconduct to the compliance officer, who is responsible for ensuring compliance with the anti- money laundering policies and procedures, and taking appropriate corrective actions.
CAMS Certification Package - 6th Edition | ACAMS, Chapter 3: Compliance Standards for Anti-Money Laundering (AML) and Combating the Financing of Terrorism (CFT), page 97 CAMS Certifications: How to Get CAMS Certified | ACAMS, CAMS Examination Preparation, page 8 ACAMS CAMS Certification Video Training Course - Exam-Labs, Module 3: Compliance Standards for Anti-Money Laundering and Combating the Financing of Terrorism, video 3.4: Tipping Off and Confidentiality Exam CAMS: Certified Anti-Money Laundering Specialist (the 6th edition), Question 8, Answer B

The Egmont Group is a global network of 170 financial intelligence units (FIUs) that facilitate the exchange of information and cooperation among member FIUs to combat money laundering, terrorist financing, and associated predicate offences12. FIUs are national agencies that collect, analyze, and disseminate financial intelligence to relevant authorities3. The Egmont Group supports the implementation of international standardsand best practices for FIUs, provides training and technical assistance, and promotes the development of secure and effective communication channels12.
Egmont Group website
Egmont Group of Financial Intelligence Units - Wikipedia
ACAMS CAMS Study Guide (the 6thedition), Chapter 5: The Role of the Financial Intelligence Unit in Combating Money Laundering and Terrorist Financing, page 1532