Conditional formatting for alternating groups of duplicated cells - google-sheets

Question

I am trying to get a conditional formatting formula that highlights groups of duplicated cells in a column, but that also differentiates among them.
When I use the formula =COUNTIF($J:$J,J1)>1, I get:
123 (green)
123 (green)
345
567
765 (green)
765 (green)
812 (green)
812 (green)
876
But I want something more like:
123 (green)
123 (green)
345
567
765 (yellow)
765 (yellow)
812 (red) (or green again)
812 (red) (or green again)
876
I don’t necessarily need different colors for each group (although that would be really nice), but at least two colors that alternate between the groups, so I can't easily visually differentiate between two adjacent group of duplicated cells.
For that last part, I am working with the formula =isodd(match($J2,unique($J$2:$J))) (plus one with iseven to use it with another color), the problem with this one is that it also highlights unique cells (which I don’t want).
Is there is a way to combine the two or another formula altogether that accomplish this?

Answer 1

Add this script and your sheet will highlight duplicated rows.
It automatically updates every time you edit the sheet.
So you can insert rows, or add rows or change rows and it will still update correctly.
You can look up how to install the script, but its easy. Let me know if stuck.
function onEdit() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheet = ss.getActiveSheet();
var lastRow = sheet.getLastRow();
var range = sheet.getRange(1,1,lastRow);
sheet.getRange("A1:A").setBackground("white");
var rowValues = range.getValues();
var color1 = "#DBAB30"; // light yellow
var color2= "#3DA843"; // light green
var color = color1;
if (lastRow < 2) return; // do nothing if only 1 row.
var dupCount=0;
var row;
for (row=1; row<=lastRow; row++)
{
if (row == lastRow){ // check if past the last row.
applyBackground(row-1,dupCount);
}
else{
if (rowValues[row][0] == rowValues[row-1][0])
{
dupCount++;
}
else
{
applyBackground(row-1,dupCount);
dupCount=0;
}
} // end if not last row
} // end loop
function applyBackground(row,dupCount){
if (dupCount > 0)
{
var colorRange = sheet.getRange(row-dupCount+1,1,dupCount+1);
colorRange.setBackground(color);
if (color == color1) {color = color2} else {color=color1};
}
}
}
Produces this output:
Which I think is what you asked for?

Answer 2

This isn't quite what you're looking for, but you can apply this formula starting in row 2 to identify the odd groups:
=and(or(A2=A1,A2=A3),isodd(sumproduct((A$1:A1<>A$2:A2)*(A$2:A2=A$3:A3))))
and similarly for the even groups:
=and(or(A2=A1,A2=A3),iseven(sumproduct((A$1:A1<>A$2:A2)*(A$2:A2=A$3:A3))))
If you tried to apply this to row 1, you would get a #REF! error. The only way I could come up with to identify a repeated value starting in row 1 was to add a third rule applied to the whole range:
=and(A$1=A$2,countif(A$1:A1,"<>"&A1)=0)
and to modify the original formulas to
=and(or(A2=A1,A2=A3),isodd(sumproduct((A$1:A1<>A$2:A2)*(A$2:A2=A$3:A3))+(A$1=A$2)))
and
=and(or(A2=A1,A2=A3),iseven(sumproduct((A$1:A1<>A$2:A2)*(A$2:A2=A$3:A3))+(A$1=A$2)))