The rope that I use for halters, bridles, and bosals is black premium 1/4" double braided polyester marine rope.  Leads and reins are made out of black Samson EQ 1/2" double braided polyester rope specifically made for equestrian use.

I use quality US made 650 nylon paraline to decorate all my halters nosebands and braided knots.  Here are examples of the different colors of paracord that I offer.



 
If you want a two tone noseband like the one pictured here.
The base (bottom) color is black and the trim (top) color is gold.