Preserve Excel Format
The Preserve Excel Format option seems to work for retaining formatting done in Excel when re-opening and refreshing cube views. However, I'm finding that my data is greyed out as if invalidated upon...
Forum Discussion
There could be a default setting in the cube view in OneStream that is overriding the Preserve Excel Format option. You may want to try checking the default, row, and column settings and changing the cube view font color in OneStream. You could also try creating selections styles in excel and applying them by navigating to the OneStream tab at the top of excel > Cube Views > Selection Styles.