Thank you for your reply 🙂
Yes, the second colour is attached by drawing the yarn through the loop created by the last slip stitch of the previous round. I found that this way the colours run more evenly and you don’t get little bits of the new colour in the previous round.
I would love to see your completed heart so please don’t hesitate to send me photos, please 😉

Thanks for your comment! I think the only thing that really confused me was the color change to start a round. For the first to second round transition: Is the first loop of the new color pulled through the last loop of the old color (the one left on the hook when you complete the slip stitch) to become the first chain of the second round’s ch 3 start? Or maybe you loosely finish off round 1’s ending slip stitch, pull up a loop of the new color through the top of the stitch as usual for a previous round’s stitch, and then chain 3 afterward?

I had figured I would eventually figure it out comparing to the pictures, after trying a different overlay project. Looking again at your pattern I think I convinced myself I was more confused than I was, because the rest looks perfectly clear. Thank you again for your reply and I’m going to edit the post to be less dramatic. It is a lovely heart!