How to Use Vertex Colors as Masks in Blender

Vertex colors—referred to as Color Attributes in modern Blender releases—allow you to paint data directly onto mesh vertices to drive material properties without creating UV-unwrapped image textures. This article explains how to create a vertex color layer, paint your mask, and hook it up to the Shader Editor node tree using mix nodes and color ramps to blend materials, textures, and surface effects seamlessly.

Step 1: Create and Paint the Color Attribute

  1. Select your object in the 3D Viewport.
  2. In the Data Properties tab (green triangle icon), expand the Color Attributes panel and click the + button to create a new attribute layer (set the domain to Corner or Point, and data type to Color).
  3. Switch from Object Mode to Vertex Paint mode using the top-left mode dropdown.
  4. Choose a brush color. For a standard binary mask, use black (#000000) for the base and white (#FFFFFF) for the masked areas.
  5. Paint directly onto the mesh.

Step 2: Add the Attribute Node in the Shader Editor

  1. Switch to the Shading workspace or open a Shader Editor window.
  2. Ensure your object has a material assigned.
  3. Press Shift + A and navigate to Input > Color Attribute.
  4. In the Color Attribute node, click the field next to the color icon and select the name of the attribute you created in Step 1.

Step 3: Connect the Mask to Drive Shaders or Textures

Depending on what you want to blend, connect the node output to a Factor (Fac) input:

  • To blend two colors/textures: Add a Mix Color node (Shift + A > Color > Mix Color). Connect the Color output of the Color Attribute node to the Factor socket. Plug Texture A into input A and Texture B into input B. Connect the Result to your Principled BSDF's Base Color.
  • To blend two entire materials: Add a Mix Shader node (Shift + A > Shader > Mix Shader). Connect the Color output of the Color Attribute node to the Fac input. Plug Shader 1 into the top shader input and Shader 2 into the bottom shader input.

Step 4: Fine-Tune Mask Contrast

Vertex colors interpolate smoothly between vertices. To sharpen or adjust the falloff:

  1. Insert a Color Ramp node (Shift + A > Converter > Color Ramp) between the Color Attribute node and the Factor socket.
  2. Move the black and white stops closer together to create a harder, more defined transition edge, or change the interpolation type to Constant for sharp borders.

Advanced: Using Multiple Masks from One Layer

You can pack three separate masks into a single color attribute by painting pure Red, Green, and Blue channels. In the Shader Editor, route the Color Attribute output into a Separate Color node (Shift + A > Converter > Separate Color). The Red, Green, and Blue outputs will each function as an independent grayscale mask factor.