Final answer:
The appropriate size roller for applying color topping can vary, but a common choice is a 9-inch roller, especially for large and flat surfaces.
Step-by-step explanation:
When applying color topping with rollers, the size of the roller to be used depends on the specific characteristics of the painting job, including the surface area and texture of the wall. Generally, a 9-inch roller is the most common size used for large, flat areas as it provides a good balance between coverage and ease of use. For smaller, more precise areas or for surfaces with more texture, a smaller or more specialized roller may be more effective. It's important to select a roller that will help achieve a uniform application of paint without too much stippling (texture from the roller).