The VRayColor texture map can be used to set any custom color and also allows you to set a floating point value for the R, G, B, A channels. It can also be used to specify overall opacity for VRayMtl materials. In the example shown, the Color is set to blue.

Color mode – Specifies the mode in which the color will be determined:   

Color – The color is directly specified by the Color parameter.
Temperature – The color temperature (in Kelvin) is specified by the Temperature parameter. 

Temperature – Specifies the color temperature value in Kelvin when the Temperature Color mode is selected.

Red – The value for the Red channel. Note that the full intensity is reached at 1.0 for this parameter (and not at 255). 

Green – The value for the Green channel. Note that the full intensity is reached at 1.0 for this parameter (and not at 255). 

Blue– The value for the Blue channel. Note that the full intensity is reached at 1.0 for this parameter (and not at 255).

RGB multiplier – The multiplier for the color.

Alpha – The value for the Alpha channel. Note that the full intensity is reached at 1.0 for this parameter (and not at 255). 

Color – A swatch used to visualize the resulting color. Double-click it to bring up the standard 3ds Max color picker. Note, however, that the color picker is limited internally to a precision of 8 bits per channel and if modifying the color, the RGB components snap to the nearest 8-bit level. 

Color gamma – A gamma correction that is applied during rendering but does not affect the Color swatch.

RGB primaries – Specifies management for the VRayColor values.

None – Values are used directly.
sRGB primaries – Values are considered in sRGB color space.
ACEScg primaries – Values are considered in ACEScg color space.