Multi-coloring: compare separate color chains
Multi-coloring extends simple coloring by keeping separate two-color components for the same digit until they interact.
Key idea
When a color in one component sees a color in another, their opposites become linked; a candidate that sees the resulting true alternatives can be removed.
See the move, step by step
Compare separate candidate-7 pairs in rows 1 and 4.
Step 1 of 4
Build separate components
Follow candidate 7 through conjugate pairs, without pretending disconnected pairs belong to one chain.
Step 2 of 4
Assign colors within each component
Row 1 uses gold at R1C1 and blue at R1C6; row 4 uses purple at R4C6 and teal at R4C2. R1C6 and R4C6 share column 6, so their 7s cannot both be true.
Step 3 of 4
Use the interaction
At least one of R1C1 and R4C2 must be 7: otherwise both column-6 endpoints would be 7. R2C2 sees R1C1 in box 1 and R4C2 in column 2, so remove its 7.
Step 4 of 4
Keep component identities intact
Remove 7 from R2C2, leaving 1 and 5. Keep the components separate: R1C1 and R4C2 can both be 7, so the two pairs are not one alternating strong-link chain.
Try it on today's puzzle
Use distinct color pairs for disconnected components. Only combine their implications when you can point to a real peer relationship between them.
Play today