Both looks are intentional — not a glitch.
Grey text = already in a report. When you create a report (via Create Report), ExpenseBot greys those rows and stamps the date in the Submit Date column (column W, on the far right). It shows at a glance what's already been reported and what's still available to report.
Grey text with a line through it = omitted. When you Omit an expense in Review expenses (a duplicate, or something you already entered in your accounting software by hand), its row stays in your sheet for your records, shown grey with a line through it. Omitted expenses stay out of reports, totals and accounting pushes. Restore it from the Omitted tab and the line goes away (the row stays grey only if it's already in a report). Expenses omitted before this was added may not show the line; the Omitted tab is the full list.
Is it safe to change the colour? Yes — formatting won't break anything. It's only a visual cue: the Submit Date in column W is the record of what's been reported, and the Omitted tab is the record of what's omitted. Removing the line by hand doesn't restore an expense — use Restore.
See How does the Review Expenses screen relate to my Google Sheet for how these rows connect to the Review screen's "In reports" and "Omitted" tabs.