Just a Note for myself to remember how to Colorize Machines

Iron -> Bronze
GIMP Colorize  30, 100, -40

Bronze -> Steel
GIMP Colorize 240,  10, -30

Bronze -> Brass
GIMP Colorize  40, 100,   0

Brass -> Electrum
GIMP Colorize  50,  60,  30

Steel -> Tungstensteel
GIMP Colorize 220,  50, -40