To put the safety dot back in, or sight dots for that matter- swab the simple with acetone to ensure it is free of oil. Then take a little dot of red or whatever color nail polish on the tip of a toothpick. Touch it right to the center of the dot and the paint will flow out and fill the cavity nicely.
I thought I'd add a couple of thoughts about finishes here without wanting to deride anybody's decisions or choices.
Cold blue can be a nice success, as evidenced by Tim's photos and don't require a lot of extras besides some steel wool and stripping compounds. The Oxpho works well and is easy to use. The outcome will only be as good as the surface prep. It is, however, more of a surface color or staining and can wear pretty easily. It'll also touch up easily.
Spray finishes require a bit more surface prep to give the finish something to bind with. I recently saw a home job that wasn't holding up very well because they'd only rough sanded the parts. The cerakote that was used really needed to have a blasted surface for uniform adhesion. I'd also guess that he probably didn't cure it properly, either.
Hot bluing is intensive in labor, equipment, and chemicals. And probably best left to professionals.
Slow rust bluing or browning will create a beautiful, traditional metal oxide finish that does a bit more than simply stain the surface. But the prep work must be meticulous and handling during the process is critical. It doesn't take a lot of equipment or chemicals but it can be sensitive to error. Do the homework before embarking on this but don't shy away either. The result can be very rewarding.
Be wary of internet shortcuts. There are some other solutions available for parkerizing or what not but if you undestand what the true process is you'll understand why diy shortcuts, even the commercially marketed ones, are sometimes best left behind.
Take some time, do some research, ask some questions, and you'll have a fantastic project!
