On Using Concealer
The first thing to remember is that a concealer is meant to correct, not cover discolorations.
For discoloration, apply Mary Kay Signature Concealer before the foundation.
For blemishes, apply a matched concealer over the foundation.
Yellow will correct red, purple and brown.
You should use concealer only on discolored skin areas. Applying to surrounding areas will create a ‘halo’ effect (normal skin color does not need correcting).
Also remember that concealer is dryer than foundation so it adheres better and will emphasize lines.
Information gleaned from Mary Kay literature