Decals have material properties similar to all other materials, but they also have a decal texture (an image map) and a texture location (represented by the decal grip). Each of these properties affects the appearance of a decal on objects.
You must select the grip for the decal to edit its properties. Selecting an object with a decal will not select the decal, and editing its material properties will change the underlying “base” material. (For more information, see Select and re-order decals.)
Darker areas of the decal image map produce a transparent material, while brighter areas create a more opaque appearance. (White shows 100% of the decal material, and black shows the material below.)
For recommendations on the size, file type, and optimization of your decal texture image, see Decal texture image recommendations.
For more information on mapping this texture on your object, see Use image maps.
Change common material properties
The Material Properties window appears.
The controls available in this window are the same for all decals. As you adjust their values, you can see the decal material change in the scene.
For information on the common material parameters in this window, see Introduction to material properties.
Replace common material properties
To replace the common material properties (Color, Highlight, Reflectivity, Transparency, and Bump) of a decal, but retain the current decal image map texture and placement, apply an existing material to the decal grip.
The selected decals will now use the values of the replacement material for Color, Highlight, Reflectivity, Transparency, and Bump.