3D printed plastic rack from Eburet brand.
In the Multi/sub scene, a material that includes 11 colors provided by the manufacturer is assigned by changing the ID of the material on the object from 1 to 11, respectively, all materials in the stack are signed. The texture of the color gradient on the model is superimposed using UVWrandomizer, so when copying, the pattern on the racks will not repeat.
For Corona render, it is recommended to install a version of at least 1.5, since the glossiness of materials is configured with PBR in mind.