This answer assumes:
1. Your ID (group value) is a related-reference field table parent record value
2. That your report will always include the latest note/entry
In your Parent < Child relationship, build a summary-field to bring back the Maximum [Record ID#] from the child table. Call this field [Max Notes Rec ID#]
In your Parent < Child relationship add the new [Max Notes Rec ID#] as a Lookup field back into the child-table
In your child-table, build a formula-checkbox field [Latest Note]. Formula:
[Record ID#] = [Max Notes Rec ID#]
In your report, you can then use Row colorization on the rows where the [Latest Note] checkbox is TRUE.
