Undertint
Mix the colour you see
Free · In‑App Purchases
Identify any colour in a photo and mix it from the watercolour paints you already own. For painters who want to spend less time second-guessing and more time painting.
Undertint helps watercolour painters answer one question: how do I mix that colour, with the paints I already have?
Point Undertint at a photo. The app simplifies the image into the colours you would actually need to paint, then gives you a mixing recipe for each one, drawn from your own palette. Recipes use Kubelka-Munk pigment mixing, the same maths colour scientists use to model how watercolour pigments combine on paper. The output is a recipe you can mix at the page, not a colour you can only see on a screen.
Everything happens on your device. Photos never leave your phone. Free to try. Pro unlocks multi-paint mixing recipes and bookmarking as a one-off purchase or a monthly subscription.
Features
• Photo simplification with adjustable detail. Pull the slider down for big colour shapes, up for finer control.
• Tap any region to see the colour identified in painterly terms and a Munsell reading.
• Mixing recipes from your own paints from a catalogue of over 100 and growing.
• Dilution gradients show how a colour shifts as you add water, so you can match the value as well as the hue.
• Save value studies to your photo library to use as on-easel references.
• Bookmark the recipe you'll mix for each colour, and Undertint will use it to prioritise coherent recipes.
Who Undertint is for
Watercolourists who want to spend less time second-guessing colour mixes and more time painting.
Beginners learning what their paints can do, and experienced painters who want a quick second opinion when matching a tricky reference colour.
What Undertint isn't
Undertint isn't a digital painting app. It doesn't replace mixing on your palette. It helps you decide and learn how to mix.
About brand names
Brand and product names referenced are trademarks of their respective owners, used only so you can identify your own paints. Undertint is independent of and not affiliated with any of them.
Privacy
Undertint does not collect, transmit, or sell your data. No analytics, no advertising, no third-party SDKs, and no network requests except to Apple's App Store for purchases. Photos you import are processed on-device and never leave your phone.
Terms of use (EULA)
See: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
• Bookmark the recipe you'll actually mix for each colour. Your choice is saved for when you reopen a study.
• A bigger paint library, including the Van Gogh Pocket Box and more Daniel Smith and M. Graham colours.
• Unlock Pro your way: keep the one-off purchase, or dip your toe with a monthly subscription.
• Missing a paint? Let me know from inside the app.
• Refinements to recipe cards and general polish.
The developer, Justin Stach, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Linked to You
The following data may be collected and linked to your identity:
- Purchases
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Justin Stach
- Size
- 9.2 MB
- Category
- Graphics & Design
- Compatibility
Requires iOS 18.6 or later.
- iPhone
Requires iOS 18.6 or later. - iPad
Requires iPadOS 18.6 or later. - Apple Vision
Requires visionOS 2.6 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- In-App Purchases
Yes
- Undertint Pro $14.99
- Undertint Pro $1.99
- Copyright
- © 2026 Stach Ltd
