what does everyone use for color and flavorings? do you do the shell too or just frosting flavoring?

My question is, I’m seeing all these yummie flavors, some are liquid, some oil and some emulsion. Can someone(s) advise on which are good to use and which to avoid and why? Thank you!

Ive been attempting full macarons for years 🫩 thanks for accepting me in here, i hope to improve with you all