Possible Clues:

• The horse starts till all is blue & Co. symbolically
• An officer on a horse shows his metal
• A blue color
• Metal that gave its name to a shade of blue
• Type of blue round object given to one officer -- there's no justice
• Deep shade of 16 dn
• Metal in gun used to hold up sailor
• Cabot left to travel the blue
• Silver-white metallic element
• No. 27, as Latvian to Lithuanian