You can highlight a single color but that's it. I'm not sure what you mean by "Design Center".
This product is designed to aid in the creation of a pattern. Using it for actual stitching is a secondary effect. It is more common to print off the pattern in a grid size that you can easily use for actual stitching than to read it during stitching.
You might be able to make a copy of the pattern and then modify the stitches as you complete them but that would require marking separate sections to avoid changes affecting areas not yet stitched.
What I do is add a color from the pattern that stands out from the rest of the colors, then give it the same symbol of the color I want to highlight. Then I replace the color I stitched with the contrasting color.