The Environment section in V-Ray render parameters is where you can specify a color and a texture map to be used during GI and reflection/refraction calculations. If you don't specify a color/map then the background color and map specified in the 3ds Max Environment dialog will be used by default.

UI Path: ||Render Setup window|| > V-Ray tab > Environment rollout (Renderer set to V-Ray)

This group overrides the 3ds Max Environment settings for indirect illumination calculations. The effect of changing the GI environment is similar to skylight.

On – Turns on and off the GI environment override.

Color – Specifies the environment (skylight) color. Note that this is ignored if there is an environment texture specified.

Multiplier – A multiplier for the color value. Note that the multiplier does not affect the environment texture (if present). Use an Output map to control the brightness of the environment map if the map itself doesn't have brightness controls.

Texture – Lets you choose a GI environment texture. Note that if present, the texture overrides the specified Color.

This group overrides the 3ds Max Environment settings when reflections and refractions are calculated. Note that you can also override the reflection/refraction environment on a per material basis (see VRayMtl) or a per map basis. If you do not enable the Refraction override, this group of controls affects both reflections and refractions. If you enable the Refraction override, then this group affects only reflections.

On – When enabled, V-Ray uses the specified Color and Texture during reflection/refraction calculations.

Color – Specifies the environment color for reflections/refractions. This is ignored, if there is an environment texture specified.

Multiplier – A multiplier for the color value. Note that the multiplier does not affect the environment texture (if present). Use an Output map to control the brightness of the environment map, if the map itself does not have brightness controls.

Texture – Lets you choose an environment texture. Note that if specified, this texture overrides the Color.

This group overrides the environment for refraction rays only. When this override is disabled, V-Ray uses the environment specified in the Reflection/refraction group when calculating refractions.

On – Enables the refraction environment override.

Color – Specifies the environment color for refractions. This color is ignored if there is an environment texture specified.

Multiplier – A multiplier for the Color value. Note that the multiplier doesn't affect the environment texture (if present). Use an Output map to control the brightness of the environment map, if the map itself doesn't have brightness controls.

Texture – Specifies the environment texture for refractions. Note that, if present, this texture overrides the specified Color.

This group controls the appearance of matte objects in reflections/refractions.

On – When enabled, V-Ray uses the specified Color and Texture during reflection/refraction calculations.

Color – Specifies the environment color for reflections/refractions. This is ignored, if there is an environment texture specified.

Multiplier – A multiplier for the color value. Note that the multiplier doesn't affect the environment texture (if present). Use an Output map to control the brightness of the environment map, if the map itself doesn't have brightness controls.

Texture – Lets you choose an environment texture texture. Note that if specified, this texture overrides the Color.