Normal dress for the rich in the 17th and 18th century had gold and silver lace to reflect their wealth. Uniforms from that early period, before they became more practical, copied those conventions, especially as officers bought their commissions and often paid for their regiment's kit out of their own pocket. Officers had silver and gold lace, troops had white or yellow. Patterns emerged to distinguish different regiments or to show off or to reflect honours awarded. The German army still has that pattern on their uniforms, the colour in the centre of the litzen shows what branch. Infantry white, cavalry yellow, tanks pink etc.