The Role of Government Guidance in Public Sector Project Delivery

Working in central and local government means navigating a wide range of official guidance. These documents outline how public sector projects should be funded, managed, and evaluated.

Known by their colour-coded names, these guidance books are essential tools. They help ensure a consistent, transparent, and high-quality approach to project delivery across government.

These publications act as best practice manuals for all 24 central government departments and executive agencies. They apply to initiatives of all sizes—from small IT projects to multi-million-pound infrastructure programmes.

For PMOs, these resources are more than background reading. A well-informed PMO that aligns with this guidance will support delivery teams more effectively and ensure governance expectations are met.

The Five Key Government Guidance Books

The core guidance books—each named by colour—cover a range of key areas in public sector delivery:

The Green Book – Appraisal and evaluation in central government
The Orange Book – Principles and concepts of risk management
The Aqua Book – Producing high-quality analysis for government
The Magenta Book – Guidance on government evaluation
The Teal Book – The definitive reference on project delivery

This article focuses on the Green, Orange, and Teal Books—as these are the most relevant for PMO functions and Microsoft Project for the web deployments.

The Green Book – Appraising Projects and Building the Business Case

The Green Book is central to public sector project development. It guides departments on how to appraise policies and evaluate programmes. Its aim is to make decisions transparent, consistent, and based on evidence.

At the heart of the Green Book is the Five Case Model. This model allows decision-makers to compare delivery options and select the best one with confidence.

Paul Dakin, founder of Demystify, provides a detailed and useful summary of the Green Book. His firm helps departments manage business case development more effectively.

The Five Case Model includes:

Strategic Case – Why the project is needed
Economic Case – Which option offers the best value
Commercial Case – Whether the procurement is viable
Financial Case – If the proposal is affordable
Management Case – How the project will be delivered and assured

This model supports the development of a robust business case at every stage—from initial concept to the Full Business Case (FBC). It aligns with PRINCE2 and is most suited to waterfall delivery approaches.

Supporting Guidance and Resources

Most public sector projects now require formal business cases that justify spending. These include cost-benefit analyses covering financial, societal, and environmental impacts.

An excellent starting point is the plain-language guide:
Assessing Business Case – A Short Plain English Guide
For agile projects—especially digital ones—departments should refer to Cabinet Office guidance. These projects typically require a Spend Controls Form submitted to the Government Digital Service (GDS).
Spend Controls Form & Agile IT Project Guidance

This ensures that even iterative, agile projects meet high standards and receive the approvals they need.

What’s New in the Green Book? (May 2024 Update)

The Green Book was updated in May 2024. The changes reflect the government’s wider focus on social equity, regional investment, and environmental sustainability.

Key changes include:

More emphasis on wellbeing and social value
Greater focus on deprived regions and levelling up
Stronger evaluation tools for measuring impact
New guidance on including environmental outcomes in investment decisions

Now, funding decisions must consider how they benefit under-served communities, not just national growth metrics.

For PMOs, this adds a new dimension to business case development. Teams must now demonstrate social and regional impact in a way that is measurable and aligned with HMT priorities.

The Orange Book – Managing Risk in Government Projects

The Orange Book outlines how government departments and public bodies should manage risk. It offers key principles that build a strong risk culture and enable strategic project planning.

It supports a culture that is:

Open and transparent
Collaborative and inclusive
Aligned with business goals

The Orange Book aligns with AXELOS’s Management of Risk (MoR) framework and promotes both top-down and bottom-up risk engagement.

The Three Lines of Defence Model

To implement risk effectively, the Orange Book recommends the “three lines of defence” approach:

First Line – Operational management and internal controls
Second Line – Oversight functions like governance and risk teams
Third Line – Independent assurance bodies (e.g. NAO, IPA audits)

This layered model helps identify, manage, and escalate risks effectively throughout the project lifecycle.

How PMOs Use the Orange Book

For PMOs, the Orange Book is an essential resource. It supports:

Proactive risk identification
Early mitigation and escalation
Development of structured risk registers
Clear communication with governance teams

By embedding this guidance, PMOs help reduce surprises and improve delivery performance.

The Teal Book – Setting the New Standard for Project Delivery

The Teal Book, published in April 2025, is the latest in the series. It sets a new benchmark for project delivery across the UK government.

Described as the “definitive guide for successful project delivery,” it provides a clear framework for all public sector professionals working in transformation and change.

The Teal Book Includes:

Best Practices – What has worked across government
Principles – The core values driving delivery
Processes – Standard procedures and expectations

It is aligned with the Government Functional Standard for Project Delivery (GovS002), which ensures that teams across departments use a consistent language and approach.

Why the Teal Book Matters for PMOs

Whether overseeing enterprise portfolios or departmental-level initiatives, PMOs can apply the Teal Book to:

Strengthen assurance processes
Align governance and delivery
Improve consistency and transparency
Support Agile and hybrid delivery models

This guidance also promotes collaboration, continuous learning, and capability development—key themes for a modern, value-adding PMO.

PMOs as Strategic Enablers

The Green, Orange, and Teal Books are more than theoretical tools. They offer real-world frameworks that PMOs can use to add value and mature their service offerings.

When PMOs align with these books, they can: