Sudoku technique guide

Grouped Colouring Sudoku Technique

Grouped Colouring extends colouring by treating grouped candidates as part of the chain. This guide explains the idea in plain English, when to look for it, and the common mistake to avoid.

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At a glance

Difficulty

Advanced

This is where Grouped Colouring normally sits in a human solving path.

Family

Visual chain techniques

It belongs to the visual chain techniques group of Sudoku logic.

Main action

Usually remove candidates

Most technique moves reduce notes first. That often reveals a simpler placement afterwards.

What is Grouped Colouring?

Grouped Colouring extends colouring by treating grouped candidates as part of the chain.

The important thing is that this is logic, not guessing. You are using the current candidates to prove that a number must either go in one place, or cannot stay in another place.

In SudoSketch, this technique is designed to work with notes and Coach highlighting, so the key cells and removal cells can be shown clearly.

How Grouped Colouring works

Focus on one candidate.
Treat a small group of candidate positions as one chain node when they act together.
Use colours to prove a grouped conflict or outside elimination.

When to look for it

Look for Grouped Colouring after easier moves have stopped working. First check for naked singles, hidden singles, locked candidates and simple pairs. If those do not move the puzzle forward, this technique may be worth checking.

For learning, do not try to scan for every advanced technique at once. Pick one method, understand the shape, and practise spotting that one pattern.

Common mistake

Grouped candidates must behave as one logical group. Do not group cells just because they are nearby.

If you are unsure, rebuild the candidates first. Bad notes create bad logic, and Sudoku will absolutely punish you for it like a tiny spreadsheet goblin.

Grouped Colouring FAQ

What is Grouped Colouring in Sudoku?