this video tutorial which demonstrates how to add a third color to the project. Most mosaic crochet only uses two colors, but occasionally you will have a pattern that calls for another color. The video works through the Flower Lattice 2 practice pattern. You can find the pattern on this blog here for free.
Before working through this tutorial you'll want to familiarize yourself with some of the mosaic crochet basics. It may be helpful to watch some of the previous videos in this series including the Foundation i-Cord Tutorial, the Foundation Single Crochet Tutorial, and the Overlay Mosaic Crochet Tutorial that works through row 6 of this pattern.
Overlay Mosaic Crochet Tutorial - Adding a Third Color: