--- title: "Simple Coloring: Follow one digit in two groups" description: "Simple Coloring follows strong links for one digit. When an area has exactly two places for it, one must be true. Alternating groups show those dependencies." lang: "en" canonical: "https://unisu-sudoku.app/en/sudoku-techniques/simple-coloring/" --- [Back to the learning guides](https://unisu-sudoku.app/en/learn/) Advanced techniques # Simple Coloring: Follow one digit in two groups Simple Coloring follows strong links for one digit. When an area has exactly two places for it, one must be true. Alternating groups show those dependencies. ![Unisu lesson on Simple Coloring, showing the explained grid](https://unisu-sudoku.app/_astro/en.TlwTXaBD_21BDVt.webp) Simple Coloring follows strong links for one digit. When an area has exactly two places for it, one must be true. Alternating groups show those dependencies. Two cells see each other when they share a row, column or 3×3 box. An elimination needs the specific visibility relationships described in the reasoning. ## An example from the app We focus only on 1. The highlighted cells are connected by links with exactly two possible positions. Exactly one side of each link must be true. For 1, the chain is C7–F7–D9–D2: each link joins the only two positions in its row, box or column. Group A contains C7 and D9; group B contains F7 and D2. The linked possibilities alternate between A and B. One group is true and the other false. Candidate 1 in C2 conflicts with at least one A cell and one B cell, so it is ruled out either way. These notes are therefore ruled out: C2: 1. The image shows the candidates relevant to this step. A note being hidden does not mean it has been logically eliminated. ## Practice the next step A cell that sees both groups cannot hold the digit. If two candidates in one group conflict, that group is false. Color displays the reasoning; it does not prove it on its own. In the app, follow the reasoning in the matching lesson and try a task yourself. With a new puzzle, always start from its actual candidate state. ## Questions about Simple Coloring ### What do the two colors represent? Two opposing possibilities within one connected chain for a single digit. They do not represent two different digits. ### Which links can I color? In this method, strong links: an area has exactly two possible positions for the digit. ### Why eliminate a candidate that sees both colors? One color group must be true. A candidate conflicting with a member of each group is excluded either way. ### Can one coloring mix several digits? This explanation follows one digit. Chains that change digits belong to other methods, such as AIC. ### Can I simply merge separate color chains? No. Without a proven connection, their color assignments are independent. Matching colors alone establish no relationship. ## Keep practicing in Unisu Download Unisu for iPhone or Android. Solve a puzzle or work through a guided lesson on the technique. - [Download on the App Store](https://apps.apple.com/us/app/id6775824061?l=en) - [Get it on Google Play](https://play.google.com/store/apps/details?id=app.unisu.sudoku&hl=en) ## Useful before this guide ### Hidden Single [Read more: Hidden Single](https://unisu-sudoku.app/en/sudoku-techniques/hidden-single/) ### X-Wing [Read more: X-Wing](https://unisu-sudoku.app/en/sudoku-techniques/x-wing/) ## Where to go next Master class Unisu · Oct 27, 2026 ### [AIC: Alternate strong and weak links](https://unisu-sudoku.app/en/sudoku-techniques/aic/) An AIC connects candidates using alternating strong and weak relationships. An assumption can then be followed along the chain to a certain deduction. Unisu ### [Learn Sudoku: a path from rules to techniques – Unisu](https://unisu-sudoku.app/en/learn/) Start with the rules, get comfortable with pencil marks and choose a technique for the situation you’re working on. Download app ## Ready for a puzzle? Take a moment. Download Unisu on your phone. Start a Sudoku or choose a lesson on the technique you want to understand. - [Download on the App Store](https://apps.apple.com/us/app/id6775824061?l=en) - [Get it on Google Play](https://play.google.com/store/apps/details?id=app.unisu.sudoku&hl=en) ![The daily challenge in Unisu](https://unisu-sudoku.app/_astro/en.C-sYR9hJ_1QwI9G.webp) ![A classic Sudoku game in Unisu](https://unisu-sudoku.app/_astro/en.C6DJ1kiE_2dRWDN.webp)