You see embroidery designs come in many forms and formats. Most of my embroidery designs are considered "In The Hoop" and small enough to make multiples in one hoop. Many embroidery machines come with even larger hoops and stitchers like to create even more multiples than the ones I provide for you in my zip files. I must use "off" colors to prevent things like too many steps combining when you sort colors and also to keep steps in the required order they need to stitch. Here's a few examples.
Let's say you open a Buggalena design that has eyes, you want it to stitch the white of the eyes first, then the center of the eye then the white "twinkle" of the eye should it have one. If I made both the white of the eye and the "twinkle" both white then when we create multiples and sort colors those steps would no longer be separated. In turn, that would ruin the finished look of the design.
In my BuggaBands you will see the final outline have two steps, typically two lines of bright green stitches (sometimes they are another color but I do try to stick to bright green) followed by the rest of the outline. If I didn't change one of those colors to an "off" color then those steps would merge together and you would not be able to see where you need to add your backing fabric.
You will also sometimes see an off color on the outlines of some felties and pencil toppers; most especially if you see the design has almost a whole double outline. Often these are meant to be "invisible" outlines. You would match those outlines to the colors of your fabric to let the inner design stand out adding your back fabric right before stitching those.
IMPORTANT TIP: Always check the Buggalena website before stitching to get examples of colors to use and to see how the final design should look after stitching. It really helps. Even I go reference it myself when stitching! LOL
I hope that helps, please leave a comment should you have any questions and be sure to join our Facebook group and ask any questions you may need to there!
As always, "May Your Bobbin Always be Full"
PS: Note, some formats automatically change all of the design colors to whacky ones. I haven't found an option to prevent that for some formats yet. Again, please reference the website. :)