The Particle Sampler Texture reads the attributes of the particle system, such as the particles' color, age, velocity, etc, and outputs the data to a material that can be assigned to the V-Ray Particles Geometry that shades the particles. This allows per-particle shading and/or adjustments.

UI Path: Texture > plugins > V-Ray > VRayParticleSamplerTexture

Default Color – Assigns the default color, which is rendered if the Default Output type is selected.

Texture – Allows a texture file to be applied. Use the Mix Strength parameter to blend between the Texture and the Default Color.

Output – Defines which channel from the particle system is used to derive data. The texture takes the value as is, i.e., if the value is a number or a color, it can only be connected to an Output type of the same kind. The texture applies the value to the material slot it is assigned to.

Default – This option applies the Default Color when there is no color information available from the linked particles.
Color – Takes the color of the particles and applies it to the texture.
Acceleration – Takes the particles' acceleration value and applies it to the texture.
Velocity – Takes the value of the particles' velocity(speed) value and outputs it through the texture.
Age – Takes the particles' age value and outputs it through the texture.
Lifespan – Takes the value of the particles' lifespan attribute and outputs it through the texture.