P: PS 27.9.1 Color of the CMYK color swatch changes after restarting the app

That issue is caused by a bug in Photoshop 27.9.1 or 27.10.

For now, it seems the only option is to revert to version 27.8 or earlier.

This has been merged into the wrong thread, but please also refer to the answers provided by acrerake and silk-m .

Here are the details to reproduce the issue:

Steps to Reproduce:

1. Create or open a CMYK document in Photoshop on macOS.

2. Define a custom CMYK color swatch (e.g., using pure channel values like C0 M8 Y100 K0) and save it to the Swatches panel.

3. Verify the swatch: The Info panel and the color applied to the artwork maintain the correct, original values.

4. Trigger a break in continuity using either of the following actions:

   • Scenario A (Restart): Close Photoshop completely and reopen the application.

   • Scenario B (Export): Export the Swatches panel to an .ase or .aco file, and then re-import that same file back into Photoshop.

Expected Behavior:

The swatch should retain its exact, unaltered CMYK numerical values across application restarts and file exports/imports, exactly as it behaves on Windows.

Actual Behavior:

1. Upon Restart: The stored swatches in the panel automatically alter their values due to an unintended forced conversion to RGB. Even when viewed or forced back into CMYK display mode, the numerical values are completely skewed and incorrect.

2. Upon Export/Import: Exporting the swatches corrupts the data upon writing the file. When re-importing the exported file, the values are already scrambled/converted.

3. Note: The artwork itself is not retroactively affected if the correct color was already painted; the corruption is isolated strictly to the Swatches panel and the swatch data management.

Cross-Platform Comparison (Control Test):

• Windows: Everything works flawlessly. Saving CMYK swatches, closing/reopening the app, and exporting/importing .ase files preserves the exact numerical values without any conversion.

• macOS: If you take a swatch file successfully exported from a Windows machine and import it into the Mac version of Photoshop, it remains intact. However, creating or re-exporting swatches natively on macOS triggers the bug immediately.

Environment:

• Application: Adobe Photoshop (macOS version)

• Operating System: macOS (Apple Silicon / Mac)

Hi All! The team has been made aware of this issue. Thanks for adding your votes.

Best, 
Sameer K.

確認しました。

スウォッチを追加しなくても確認できます。

・全てのスウォッチを削除する

・デフォルトスウォッチを追加する

このとき、CMYKグループのスウォッチは正しいCMYK値になっています。

M100/Y100等。

・Photoshopを再起動すると、CMYKグループのスウォッチも数値変更されます

CMYK=2/97/98/0

等。