After the leather dried, I painted it with acrylic paint.  They do sell dyes for leather, but the guy at Tandy, who was perfectly willing to sell me hundreds of dollars of crap I don’t need, said that acrylic would work just fine.

I first painted the sun red, then painted over it with gold interference paint.  So now it looks gold directly, and red when you see it at an angle.  The moons and oak leaves also have interference paint.  Not shown, gold leaf stars on the spine.