Choosing the right color in a tinted lip serum can be a fun yet challenging task due to the plethora of options available. Here are some factors to consider:

1. Skin Undertone: The first step is to identify your skin's undertone. People usually have cool, warm, or neutral undertones. Cool undertones lean towards pink, red, or blueish hues. Warm undertones are more yellow, peachy, or golden. Neutral is a mix of warm and cool.

2. Natural Lip Color: Your natural lip color also plays a significant role in choosing the right tinted lip serum. For instance, if you have naturally pigmented lips, you might want to opt for deeper shades.

3. Occasion: The occasion or event you're attending can also dictate the color of your lip serum. For a casual day out, you might want to stick to neutral or lighter shades. For a night out or a formal event, you might want to go for bolder, deeper shades.

4. Personal Preference: Ultimately, your personal preference plays the most significant role. If you feel confident and comfortable in a particular color, that's the one for you.

5. Experiment: Don't be afraid to experiment. Trying out different shades can help you find the ones that suit you best.

Remember, the right color should enhance your natural beauty, not overpower it. And always consider the ingredients of the lip serum. Look for hydrating ingredients like hyaluronic acid, Vitamin E, and natural oils to keep your lips moisturized and healthy.