Colour/ Mutation Identification

[JKTM]

Good day. Once again I am asking for your expertise in identifying the mutation of my friend's pigeon. He only sent me the tail feathers picture. Hoping for your response. Thank you!

[AdamArcher]

Appears to be opal, based on the tail alone. It's always best to post more than just a tail though

[JKTM]

Thank you sir. I’ll ask for additional pictures. I’m still having a hard time differentiating dominant opal from recessive opal. Do you have any techniques or quick tips on how to properly identify and differentiate them?