Why Not Same Colors in Thread of Battery Terminal Block

 The different colors you see in the thread of the terminal block cross-section are due to the different materials used in the screw connection system.

1. The screw itself (metallic gray/golden center) This is the actual screw, typically made of steel (often with a zinc or nikel plating, which can appear silver, or brass/brone for better conductivity/corrosion resistance, whcih can appear golden)
2. The light yellow/cream-colored layer around the screw
3. The silver-gray mass on the left: This is the multi-strand copper or aluminum conductor wire that the terminal block is designed to clamp. it appears gray/siliver because of the many individual strands which are cut and compressed together in the cross-section.
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