true cobalt blue spinel is rare and very expensive. What is your budget and what size are you looking for?
I think there a difference between cobalt blue spinel and true cobalt spinel and it needs high-end testing.
“Cobalt blue” is a misnomer. It simply means that the Spinel looks cobalt colored, but doesn’t necessarily contain that element. It’s more of a marketing ploy like “pigeon blood.” There are no restrictions on using that term and I’ve seen very grey spinels described as cobalt blue. “Cobalt spinel” means that the stone actually has been confirmed to contain cobalt, but not all true cobalt spinels are that blue.
Regardless of the element cobalt or not, one should always evaluate the stone on its color merits.
Ha? You say there is green spinel, too? Please expand!