Highlight Group of Dates if Dates Match List of other Dates

Try

Conditional Formatting

• Highlight applicable range >> C2:C9
• Home Tab >> Styles >> Conditional Formatting
• New Rule >> Use a formula to determine which cells to format
• Edit the Rule Description: Format values where this formula is true: =COUNTIF(dates,C2)>0
• Format… [Number, Font, Border, Fill]
• OK >> OK