Here is a quick step by step on how to get the RGB information from each and every particle in maya and use it in vray for whatever your heart desires.
First, select your nParticle’s and in the attribute editor go to/tick Attributes>Vray>Per-particle attribute export.
Second, scroll down to the bottom and open up the extra vray attributes, tick any boxes of information you want to use down the line e.g RGB
Third, with the particles still selected right click and assign a new material, I used the standard vrayMtl.
If you want to use the colour information just use the particleSamplerInfo node and the data will get passed through.
Below are some images to help illustrate what I done, I created a RGBPP (which isn’t there by default) by going to ‘Add dynamic attribute’>’colour’ and ticking add per particle attribute. Then right clicking on this new field found in the ‘Per particle (array) attributes’ section and putting in the random colour function as in the image.