Answer

To highlight duplicates in different colors in Excel, use Conditional Formatting with multiple rules that target specific occurrences of the same value.

Method 1: Highlight First and Subsequent Duplicates with Different Colors (Built-in Rules)

How do you highlight duplicates using Conditional Formatting?

To highlight duplicates using Conditional Formatting, apply separate rules for duplicate and unique values.

Steps (Windows and Mac)

1. Select the data range.

2. Go to Home → Conditional Formatting → Highlight Cells Rules → Duplicate Values.

3. Choose Duplicate and select the first fill color.

4. Click OK.

5. Repeat the steps.

6. Choose Unique and apply a different fill color.

Result

• All repeated values share one color.

• All single occurrences use another color.

Limitation

This method does not differentiate between the first duplicate and later duplicates.

Method 2: Highlight First Duplicate One Color and Additional Duplicates Another Color

How do you highlight first duplicates differently from additional duplicates?

To highlight first duplicates differently, create two Conditional Formatting rules using formulas.

Steps (Windows and Mac)

1. Select the data range.

2. Go to Home → Conditional Formatting → New Rule.

3. Select Use a formula to determine which cells to format.

4. Enter this formula for the first occurrence: 

   =COUNTIF($A$1:A1,A1)=1

5. Choose the first color.

6. Click OK.

7. Create a second rule.

8. Enter this formula for subsequent occurrences: 

   =COUNTIF($A$1:A1,A1)>1

9. Choose a different color.

10. Click OK.

Result

• First appearance of a value uses one color.

• Every repeated appearance uses another color.

Method 3: Highlight Each Duplicate Group with Different Colors (Advanced)

How do you assign different colors to different duplicate values?

To assign different colors to each duplicate group, use helper columns combined with Conditional Formatting.

Steps

1. Insert a helper column next to the data.

2. Use this formula to generate group numbers: 

   =MATCH(A1,UNIQUE($A$1:$A$100),0)

3. Select the original data range.

4. Create multiple Conditional Formatting rules.

5. Assign colors based on helper column values.

Result

• Each duplicated value group receives a distinct color.

• Scaling requires additional rules due to rule limits.

Windows vs Mac Differences

What is different between Windows and Mac when highlighting duplicates?

No. The Conditional Formatting interface and formulas work the same on both platforms.
Rule Manager access differs slightly in navigation, but functionality remains identical.

Common Issues and Fixes

Why are some duplicates not highlighted?

Yes. Incorrect absolute or relative cell references cause rule failures.
Use fixed ranges such as $A$1:A1 to ensure accurate evaluation.

Why do colors overlap or override each other?

Yes. Rule priority affects formatting.
Adjust rule order using Conditional Formatting → Manage Rules and place specific rules above general ones.

Best Practices for Highlighting Duplicates

1. Limit the range size to improve recalculation speed.

2. Use clear color contrast for accessibility.

3. Document rules for future maintenance.

4. Avoid excessive rules to prevent performance degradation.

Key Excel Terms Used

• Conditional Formatting

• Duplicate Values

• COUNTIF

• Helper Column

• Rule Priority

This approach ensures accurate duplicate detection, visual clarity, and scalability for large datasets.

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