Hi Jamey, yes, I was aware of the coloring of the red/orange agates thru heating in the coals, and I own a sweet "new" carnelian eye bead (no pic yet)that was overheated and created hundreds of minute fractures within the stone. A beauty to display, but I don't dare wear it.
I've colored a few reds myself this way, with varying degrees of success!
5 minutes or so in the coals, then into a warm ash pile to cool slowly.
Do you know the formula for the browns? I'd love to give it a try!
Merry Christmas and a happy holiday season to all.
Jeff

This agate eye is actually PINK overall! My daughter refuses to take it off! It was among the $5 strand from the yard sale! jl