You have probably heard of the term “fussy cutting,” particularly in reference to quilts. That is when a particular design on the fabric is strategically placed so that, when cut and stitched, it is perfectly displayed within the pieced block.
Much like a paint palette, digitizers use certain thread libraries when creating embroidery designs. Some are chosen because of the thread brand. Others are chosen as a default in the digitizing program that created them. Either way, thread stitch out charts are not necessarily like paint-by-number boards; you may choose another color if it is more to your liking or matches your fabric better.