Colors

Colors
The technique Colors is very simular to Remote Pairs. While Remote Pairs is about pairs within a cell, Colors is about pairs in a group. When there are two cells in one group (row, column of box), then one of these cells must contain this value. When multiple pairs are chained together, these candidate values can be excluded. In the example below only the candidate values 5 are visible. The colors purple and pink are assigned to every pair. When a purple cell is a 5, every purple cell must be a 5. When a pink cell is a 5, every pink cell must be a 5. If the purple cells are a 5, then the pink cells cannot be a 5 and vice versa. When a cell is in the same group as a pink and a purple marked cell, this cell cannot contain a 5. Therefore, in the example below, the candidate value 5 can be excluded from the yellow marked cell.

The example below is also very interesting. There are two cells in the same group that are marked by the same color; the two pink cells in the eighth row. Because these cells cannot both get the value 6, neither one of them can be 6. Therefore, the candidate value 6 can be excluded from these cells. Because if the purple cells are a 6, then the pink cells cannot be a 6 and vice versa, so every purple cell has to be a 6 here.