Vertex color properties, also known as color at vertices properties or CAVs, are colors stored in the polynodes (polygon nodes, or sample point) of an object. They can be used for a variety of purposes, such as storing surface color, illumination, or custom data. If necessary, you can store several vertex color properties on the same object.
Every polygon has a polynode for each of its corners, so at a given vertex there are as many polynodes as there are polygons that share that vertex. The color information is interpolated between polynodes — for example, if you paint each corner of a square polygon a different color, then the center of the polygon would display a blend of each of the four colors.
The polygonal model to the left has a base color applied to it using a Lambert surface shader. Applying a surface shader is a good way to give your model or object a background color before painting its vertices with the Color at Vertices tool.
Alternatively, you can paint every other polygon so as to avoid using a material shader.
The polygonal model to the right was given a face full of stubble using the Color at Vertices tool. A brownish color was defined and then painted directly on the model's polygons using a little transparency to blend the skin color (applied using the Lambert shader).
In this example, a combination of polygon and vertex bleeding was used.
Vertex colors are often used in games because they are an efficient way of storing color information that can be used in a variety of ways, e.g., for pre-baked lighting, texture blending, and so on.
Vertex color properties support 8-bit RGBA values, as well as HDR RGBA values.