The Random Color Shader in Octane can be a great way to assign varied colors to objects in Cinema 4D while rendering. Octane version 3 added some tweaks to the Random Color Shader that you may have noticed.
Here, GlassHand Films Artistic Director, Brandon Clements walks through how to use the Random Color Shader in Octane. Then moves on to show how to use it with X-Particles, giving you a unique color for each particle in a group.
Something in the same vein, The Pixel Lab had a look at Creating Random Colors in Cinema 4D with the Mograph Color Shader that would generate a random set of colors to Clones. Also, Ryan Snider had a look into creating a random material ID pass in Cinema 4D.