Coloring

Coloring follows conjugate links for one digit. A conjugate link exists when a house has exactly two candidates for that digit. If one endpoint is false, the other must be true, so the endpoints can be colored alternately.

When to look for it

Coloring is helpful when a digit has several strong links but no simple Skyscraper, Kite, or Turbot Fish is available.

Implemented in Xodoku

• Color Trap removes an uncolored candidate that sees both colors. One of those colors must be true, so the uncolored candidate cannot survive.
• Color Wrap removes a color when two candidates of the same color see each other. That color would place the same digit twice in one house.
• Multi Colors connects multiple coloring components and uses visibility between them to remove candidates.

Scope

Coloring is a teaching-friendly view of short single-digit chains. Some deductions may also be returned as X-Chain, Turbot Fish, or AIC when that proof is shorter or appears earlier in the strategy order.