Hmmmmmmmm, it depends on the skin Teni. You can do both.

For minor imperfections, conceal after. Let the foundation do the work for you first and then spot conceal only where you need to. You use less product and you won't be rubbing off all your hard work.

However for clients with major acne, scarring, rosacea etc I colour-correct first and then do foundation.
Agreed!