The color can be changed using CoronaSelect prepared in the material, there are 14 in total, or you can take them from the prepared spheres with individual materials.
Who works in the V-Ray version lower than 3.1, be careful, in the materials in the BRDF section there is Microfaset GTR (GGX), if your version is older than 3.1, then the BRDF field will be empty. Choose Blinn, Phong or Ward - which is preferable for you.
https://www.roche-bobois.com/en-UA/product/informel-large-3-seat-sofa