An ERA is not a car to flip, I think you are learning that the hard way. Stick to cars that are built on par ("factory" types) or down the chain with a $23K FFR. That's the reality of the market.
If you are thinking an FIA is a good candidate for flipping... I think that's even further out there.
Old car, older version, colors are not at the top of anyone's list (and I am a huge green Cobra fan). It's a buyer's world on used cars. I don't know if the changing price has anything to do with it either