I have had an inquiry about from a customer who saw some rings
online that boasted to be made of red gold. She said that it was
"blood red" in color. Is anyone aware of a gold alloy this color?
Some oxidized copper finishes might look like that, so might rose
golds in an online ad where the photographer either got the light
totally wrong, or was fooling with photoshop afterwards...
But other than that, My guess would be enamel.