Why does Color of charging terminal change and Wearable no longer charge?

Charging terminals of your device have possibility which might be damaged by foreign material, such as sweat, liquid  while it had been charged before.

Before charging the battery, ensure that the charging terminals of the wearable devices and the charging dock are free of foreign material, such as sweat, liquid, or dust. If not so, charging terminals part of your device may be damaged while charging. Clean the charging terminals with a soft dry cloth.

*Confirm the location of the charging terminals on the Gear and the charging dock and Ensure the charging terminals of the Gear and the charging dock are free of foreign material, such as sweat, liquid, or dust. Clean the charging terminals with a soft dry cloth