Try this. Grab a copper-based opaque, i.e. turquoise, sky-blue (NOT periwinkle), petroleum green - anything that reactions with ivory.
Decorate it with some intense black, frit, trails, etc.
Reduce it, or use a slightly reducing flame for the entire bead. Make sure that you get the red popping up on the turquoise or green.
Now - does the red reduction crawl over to the intense black, and form red borders for you? I've been having a lot of fun with this little reaction.
This bead is Petroleum Green and Turquoise, plus intense black frit. The reaction happened by itself - I must have been working in a reduction flame.
Same bead, other side.
This little guy was just Pet. Green + Intense Black Frit. I deliberately reduced this at the end. The red seems to have collected in the middle of the black.
Let me know if this works for you too, or whatever variations you come up with.