How to rust or blue metal doors

My name is Erick I am a contractor building a salon in Pasadena, California. My client is looking for different styles of doors to cover her cabinets. She gave me a picture of something that looked like bluing steel. I also told her about how motorcycle builders are making their tanks and fenders look like rust. Can anyone help me or tell me a step by step process on how this is down. Or where to get the additives to make the steel blue or to make it look like rust. Thank you for your time and response.

Simplest solution for rust finish is diluted muriatic acid ⇦ on eBay or Amazon [affil link] or even kitchen salt solution.Very good book for you is Angiers handbook Firearm Blueing and Browning [on eBay , Amazon, AbeBooks affil links] (15-20 USD). Hope it helps and good luck!