Color correcting products are popular at the moment.
I personally feel very few people actually need to use a separate color product to correct problems. Saying that, I would advise when using color correctors to mix them with another product, e.g. mix green with your foundation and only apply where you have redness. If you have mild redness try mixing yellow with some foundation, its easier to get right than green and has a neutralizing effect on the redness.
There are certain colors that help with different problems.
Under eye dark circles:
Warm skin use a peachy toned under eye concealer
Cool skin use a pinky toned under eye concealer
Darker skin use an orangey under eye concealer
Remember the best place to apply makeup is in nature light, especially if you are using color correcting makeup.