I made my press out of junkyard found steel so I designed it around what I had. I made my dies slightly off center to allow me to straighten my steel on flat pieces beside my dies so I didn't have to change dies every time.
I installed brass on the slide where it touches the frame to...
Awhile back I colored several blades made out of different content damascus. I brought it to a local machine shop to test the hardness and found that Ed is correct regarding the ruining of the temper. Some materials did a little better than others, but at best you are looking at low 50's on...
On that particular piece of steel I used Nitre Blue that can be purchased from Brownells. It takes a little trial and error to get the results you desire, but not at all difficult. It is important to get whatever you are coloring to be scratch free and highly polished.
I think it looks great. The only thing I would have done differently is triple the amount you made, I would want a big supply of that pattern.
Have you ever used a snagging wheel? I think they work better and faster at removing the rough fire scale.