How to fix Outlook calendar events not colour-coding or showing categories correctly in Microsoft 365

Summary

This guide helps you troubleshoot and resolve: How to fix Outlook calendar events not colour-coding or showing categories correctly in Microsoft 365. Follow the steps below to fix the issue.

Common Causes

If your Microsoft 365 Outlook calendar has stopped displaying colour-coded categories on events, appointments, or meetings, the issue is usually tied to view settings, category configuration, or a corrupted profile. This guide walks you through restoring those colours so your schedule is visually organised again.

Quick Fix Steps

Try these steps in order. Most customers find their categories return after the first two.

1. Open Outlook and switch to the Calendar view.
2. Click View > View Settings > Conditional Formatting and confirm your categories are listed and set to display in colour.
3. Click Home > Categorise > All Categories and confirm each category has a colour assigned.
4. If colours are missing, tick the box next to each category name and choose a colour from the dropdown.
5. Close and reopen Outlook, then check your calendar again.

Detailed Instructions

Check that category colours are enabled in Conditional Formatting

1. In Outlook, switch to the Calendar view.
2. Click View > View Settings.
3. In the Advanced View Settings dialog, click Conditional Formatting.
4. Under Rules, confirm each category you want displayed is listed and that Show on calendar is enabled.
5. Click Font to adjust the colour if needed, then click OK twice to save.

Restore missing category colours

1. Right-click any calendar event and choose Categorise > All Categories.
2. For any category showing No colour, click the dropdown arrow next to the category name.
3. Choose a colour, or click New to create a fresh category with a colour.
4. Click Apply, then OK.

Re-apply categories to existing events

If your categories exist but events appear uncoloured, the colour tag may have been stripped during a sync or migration.

1. Switch to Calendar view in Outlook.
2. Click View > Change View > List to see all events in a sortable list.
3. Click the Categories column header to group events by category.
4. Select the events missing a category, right-click, choose Categorise, then pick the correct category.
5. Switch back to View > Change View > Calendar to confirm colours are showing.

Reset the Outlook navigation pane

A corrupted navigation pane can hide category colours even when they are configured correctly.

1. Close Outlook completely.
2. Press Windows + R, type outlook.exe /resetnavpane, and press Enter.
3. Outlook will reopen with default navigation settings. Re-check your calendar colours.

Troubleshooting

Colours show on desktop but not on mobile

The Outlook mobile app honours categories but may display them as small dots rather than full background colours. To confirm:

• Open the event in the mobile app and check the category label at the bottom of the event details.
• If the label is missing, sign out of the Outlook mobile app and sign back in to force a category sync.

Categories reset after restarting Outlook

This usually means your Outlook profile is loading from a cached or corrupted data file.

1. Click File > Account Settings > Account Settings.
2. Select your Microsoft 365 account and click Repair.
3. Follow the prompts, then restart Outlook.

Categories missing after a mailbox migration

When mailboxes are migrated between tenants or from on-premises Exchange to Microsoft 365, category definitions sometimes fail to copy across.

1. Open Outlook on the web at https://outlook.office.com/ and check whether categories appear there.
2. If categories are missing in the web app, recreate them in Outlook on the web > Settings > Calendar > Categories.
3. Once saved in the web app, reopen the desktop Outlook client and allow up to 15 minutes for the categories to sync down.

Check for conflicting add-ins

Third-party Outlook add-ins occasionally override category rendering.

1. Click File > Options > Add-ins.
2. At the bottom, change Manage to COM Add-ins and click Go.
3. Untick any non-essential add-ins, click OK, and restart Outlook.
4. If colours return, re-enable add-ins one at a time to identify the culprit.

Rebuild the Outlook data file as a last resort

If categories still will not display after the steps above, the local data file may be corrupted.

1. Close Outlook completely.
2. Press Windows + R, type %localappdata%\Microsoft\Outlook, and press Enter to open your Outlook data folder.
3. Locate the .ost file for your Microsoft 365 account and rename it to .ost.old.
4. Reopen Outlook. A fresh .ost file will be created and synced from the server.

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