There is a difference between joining in a new color and switching colors in Crochet. The “How To – Switch Colors In Crochet” will be coming in the future :).
Joining in a new color means you have no yarn on your hook and you can choose which stitch to insert the hook into and where the new color will start.
One simple way to join a new color is to tie the new yarn around the stitch in a simple knot where you want the color to start, and then to insert the hook into the stitch and Yarn Over with the new color.
A more efficient way I use is creating a slip knot on the hook itself first and then insert the hook into the stitch space (where joining is required).
When asked to “chain 1” after join: Start with a slip knot on the hook, insert the hook in the space mentioned, Yarn over, pull through and pull through loop on hook (you created a slip stitch), and now chain one.
When asked to “1 Single Crochet in same space as join”: Start with a slip knot on the hook, insert the hook in the space mentioned, yarn over, pull through, yarn over again and pull through two loops on hook.
Now it’s easy to continue with the instructions with the new color! 🙂
Hope this helped! 😀