The "D" in "FD&C Red Dye #40" stands for "Drugs" and it means the chemical is approved for use as a colorant in drugs.

You may be wondering how a color helps the drugs work better, and we were wondering that too. The answer, it seems, is that it makes the medication more appealing and more recognizable. If a tablet, liquid or capsule is recognizably colored, it makes it more readily identifiable both during dispensing and when advertising the product.

You need to remember that medications are products just like sodas, candy bars and automobiles. There's millions and millions of dollars invested in "branding" a product to make it more recognizable and desirable, ultimately to increase sales and profits for the parent company.

There is a psychological effect of color - "active" colors such as red or yellow tend to make us feel more alert and "passive" colors such as blue or green tend to makes us feel more relaxed. Depending on the expected effect of the medication, the manufacturer may impart a color to help suggest the desired response. In reality, the color has no effect on the effectiveness of the medication, which is why it's listed under inactive ingredients on the label.