VrayMtl Color Correction is a script for 3ds Max that adds Color correction nodes to a VrayMtl and lets you tweak their settings. You can apply a correction with any specified values to any selected material slot — Diffuse, Bump, Glossiness, Translucent or Self Illumination — and the existing bitmaps are kept inside the color correct. Every parameter can be changed afterward, so you can add color correction on Diffuse and Bump at default values, then select only the Diffuse to choose a random hue, or select the Bump and Glossiness to set saturation and adjust contrast or gamma.
Randomization is built into each parameter. The randomize option sets a random value on the existing material, so all objects sharing that material receive the new color or bump value. If you need each object to get its own random value, checking "New Materials" creates one material per selected object and scatters the random values across those materials.
Installation follows the standard script method: drag and drop into the viewport, then find it under Customize, Customize User Interface, Toolbar, in the category "SimonScripts".