A conjugate pair exists when a given digit can be placed in exactly two cells of a given column, row or box. So one of these cells will get this digit, the other will not. To mark these cells, we use two different colors, coloring one cell with the first color, the opposite cell with the second color.

One cell can belong to more than one conjugate pair for the same digit. Then the conjugate pairs can be connected to form a group (cluster) of conjugate pairs. Such a group is also colored with two colors, so that each conjugate pair has different colors. The group of conjugate pairs is characterized by the fact that the digit can be placed in either all the cells colored with one color or all the cells colored with the other color. There is no other option.

Having a group of conjugate pairs, we can analyze them using techniques: