Conditional formatting formula to highlight alternate groupings of duplicate dates

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    This one has me stumped, and I'm not easily stumped.

    I have a simple column of dates; some dates are duplicated, some are not.

    What I want is to be able to highlight only the duplicated dates, in alternating fashion.

    You might think that Conditional Formatting already provides this - just go to Highlight Duplicates.

    But that will not achieve the objective since I don't want all the duplicated dates highlighted in one color.

    I want one color to highlight the first group of duplicated dates, a second color to highlight the next group of duplicated dates, then back to the 1st color for the next group, etc. An easy illustration is attached.

    Thank you !