Recently I am mapping the fire hydrants and just learned that the color indicates a different water source. For example, red=freshwater; yellow=sea water. Not knowing how useful it is, keep adding those missing info seems interesting.

Related Tags

Tag:emergency=fire_hydrant - OpenStreetMap Wiki

• type= wall / pillar
• colour= red / yellow
• ref= number

References

• 消防栓 - 維基百科，自由的百科全書
• 筲箕灣：消防栓甩晒色 造成混亂
• 香港街頭消防栓特多