Hi Julie, I remember the same thing happening when I grew balsam impatiens from seed a few years ago. I don't think they like being inside too long. Once I started hardening them off outside, and planted them, they turned green again.

The leaves that are turning yellow will fall off, and you'll probably end up with a very long stem with leaves on top. You can plant them more deeply, right up to the first set of leaves, in case you didn't already know this.

Hi Julie,
In my zone 9, I direct sow them. Here they are almost carefree with the exception of watering them often due to the heat. When I started growing them I put them in pots and agree that they didn't like it indoors. Mine all died. After that I began to sprinkle the seeds diectly in my shade bed and let them do what they do own thier own. Now I grow them every year. When they go to seed I just pop the seedheads into my flower beds and lightly cover them with soil. Before I know it I see them popping up freely on thier own again.
I love these and would eventually like to branch out into more colors.

Good Luck,
Kelly