How to Highlight Out-of-Gamut Colors in GIMP

When preparing images for print or converting between color spaces, certain colors may exceed the target color profile's reproducible range. GIMP includes built-in color management tools that identify these out-of-gamut pixels and overlay them with a distinctive warning color. This guide outlines the exact steps required to set up a target soft-proofing profile, customize your gamut check warning color, and enable the visual warning directly on your canvas.

Step 1: Set the Target Soft-Proofing Profile

Before GIMP can detect out-of-gamut colors, it needs to know your intended output profile (such as a specific CMYK printer profile).

  1. Open your image in GIMP.
  2. Go to the top menu and select Edit > Preferences.
  3. In the left panel of the Preferences dialog, click on Color Management.
  4. Set the Image display mode to Soft-proofed color display.
  5. Locate the Soft-proofing profile field, click the drop-down menu, select Select color profile from disk..., and choose the target ICC/ICM profile for your print or display medium.

Step 2: Choose a Custom Gamut Warning Color

By default, GIMP uses a neutral gray or black mask, which can blend into the image. Choosing a vibrant, contrasting color makes out-of-gamut pixels immediately visible.

  1. While still in the Edit > Preferences > Color Management tab, locate the Out-of-gamut color setting.
  2. Click the color swatch next to "Out-of-gamut color" to open the Color Chooser.
  3. Select a distinct, high-contrast color that does not appear in your composition (such as neon magenta or bright cyan).
  4. Click OK in the Color Chooser, then click OK to close the Preferences dialog.

Step 3: Enable the Gamut Check Overlay

Once configured, you must activate the gamut warning display on your current view.

  1. In the main image window, click View in the top menu bar.
  2. Navigate to Color Management.
  3. Ensure Soft-Proofing is checked (shortcut: Ctrl + Shift + Y on Linux/Windows).
  4. Check Mark Out of Gamut Colors.

Any pixels that cannot be accurately reproduced by the selected target profile will instantly be highlighted with your chosen custom warning color.

Step 4: Adjust Out-of-Gamut Pixels

To bring the highlighted areas back into gamut:

  1. Add an adjustment layer or use tools such as Colors > Hue-Saturation or Colors > Curves.
  2. Reduce the saturation or adjust the lightness of the specific color channels displaying the warning overlay.
  3. As the values fall back within the target color space, the warning color highlight will disappear in real time.