Without seeing a picture of you, I’m guessing that the grey cast could be due to a number of things. My first guess is that you’re using colors that are too light for you. Have you recently been out in the sun lately? I know that after I get a tan I have to switch out my concealers and powders – I can’t wear my MAC Blot in Medium Dark and I’ll switch out to the MAC Couture Mystery Powder, which is a deeper tone, otherwise the Blot looks too ashy. It could also be your sunscreen. Some contain titanium dioxide, which is infamous for leaving a grey cast on darker skin tones.

Another possibility is that you may also be using the wrong type of concealer on your face. I recently read in Allure magazine that you should use a thicker concealer, like Studio Finish SPF 35, Studio Stick Concealer or Studio Touch-Up Stick for pimples and other skin imperfections.

Are you using a brush to apply your product? You may want to invest in one to make your concealer look flawless. If you have brushes play with different ones to see which gives you the most natural looking application.

If you’re on a budget you could also try a few things to make it work. One is to try applying the products in natural light. If I put on my makeup in the bathroom I use too heavy a hand because the lighting is dark, but when I put makeup on in my living room, which has a lot of natural light, it usually turns out just right. The heaviness of application of the product does make a difference.

Another thing you could do is to get a trusted friend to come over and give you an honest opinion of both concealer and powder combos. I recently went to the cosmetics counter looking for an undereye concelear, and the very nice makeup artist pointed out I didn’t need one, and reminded me that the things we perceive as flaws are often just what we make them out to be because we’re always staring at ourselves and critiquing how we look.

If it turns out that all your friends are guys who know nothing about makeup and you have access to a digital camera then take pictures of yourself in natural light of the different combos and compare them to each other. Which combo makes your skin look more even? Which do you think you look prettier in?

If all else fails I’d either: 1.) go back to the old combination of NC30 Select and NC40 Studio Fix or 2.) go back to the MAC counter and get some hands on advice. Makeup is all about trial and error, and I have to say that I’ve failed many times when it comes to concealers and foundations, so I feel your pain. Good luck!