That leaf was damaged but not by the sun. May have been an insect bite or just a hole put in that leaf during transit and repotting. You can use the leaf with no problems when the plant is bigger. Try extending your watering to every other day. If the potting medium is too damp the stem and roots will rot. Too much water will also cause the leaves to change color but the plant may be running out of food. My basil leaves become lighter as the plant becomes bigger. However I plant in ground and do not fertilize.

sometimes it Take new plants a while to acclimate to their
new envronment.
You have to make sure that it is well watered after replanting(either in a bigger pot or in the garden).
Plants like basil, grown in greenhouse, are too tender and can get bruised easily in transport and handling. But they will toughen up outdoor soon.

Does basil have better flavor outdoors or indoors? I'm only able to get about 4 hours of sun where I am and it's been pretty cloudy and cold lately. I don't know if I can attribute it to the weather or the fact that I'm growing it inside, but the flavor isn't as strong as I remember basil to be...it fades pretty quickly when put in a hot dish too. Also, sometimes it produces funny aromas, like soap or a strong citrus.

Outdoors where it gets fresh air and plenty of direct sun. Some basil types have less flavor and smell, compared to others. Genovese basil is one of the short bushy types, and does great in big pots. The soil also has an effect on the quality. I also use a fertilizer suitable for herbs. It helps to increase essential oil and improves taste and smell.

I bought some starts from a grocery store and have been growing it in a soilless medium for some time...I'm pretty sure I bought sweet basil. Maybe it's just too cold and cloudy for it to develop true flavor...I don't think fertilizer has anything to do with it

Repot and yes, fertilizers can improve flavor and smell. Herbs, by themselves are mostly weeds, but because of all the culturing and breeding they have become more prominent in their characteristics. I use Garden alive fertilize for herbs and its helped to improve taste on dill, rosemary, sage, thyme, and several others. Without it, the plants are somewhat spindly. I never use any chemical fertilizers like Miracle Grow, and prefer organic based fertilizer for all of my garden. Soilless medium isn't a good substitute to continue to grow healthy plants in, as it lacks many of the essential minerals and micronutrients, not to maention regular NPK in a form that plants can absorb. The grocery store herb plants are forced grown in greenhouses, and after a short time they become leggy and really dont have the same quality as those grown from your own seeds, and planted in your own garden. There are many kinds of basil, and also many flavors and smells for the basil family. With store bought plants, you never know anything about the kind of basil it is, which could be something thats not to your taste. I don't buy plants anymore, and start all mine from seeds. That way, I now what I am growing and know what the results will be like. Basil doesn't like a lot of cool weather, but cilantro does.

If I were to grow some in a pot, what would you recommend as a potting medium?

I have purchased basil plants at my local hardware store. Every one I took to my rooftop container garden and transplanted them into a container.

Everyone has promptly rolled over and died. It's windy up there. The wind does dry out the plant, but other plants thrive.

I would love to grow some basil here. I'm spooked though.

I live on Russian Hill.

If the plants had been grown in a greenhouse or protected spot sticking them straight on the roof in wind and sun will have shocked them dramatically. Plants need to be hardened off before full time exposure to the great outdoors. Basil is really easy to grow from seed so you could start some of your own which will grow up used to your conditions.

Thanks. They were shocked dramatically. I have just started some seedlings. They will have to sprout outdoors since my apartment does not get enough light. That seems to work fine