That lighter grey text is intentional — not a glitch.
What it means: Grey rows are expenses that have already been added to a report (via Create Report). When you create a report, ExpenseBot greys those rows and stamps the date in the Submit Date column (column W, over on the far right). The grey is a visual cue so you can tell at a glance what's already been put in a report versus what's still outstanding and available to report.
Is it safe to change the colour? Yes — editing the text colour won't break anything. Just know that ExpenseBot may re-apply the grey the next time reports are generated, and those rows stay marked as already-reported regardless of what colour you set. The Submit Date in column W is the reliable record of what's been reported.
See How does the Review Expenses screen relate to my Google Sheet for how grey rows connect to the Review screen's "In reports" tab, and what happens to them if you delete or regenerate a report.