The diffuse color determines the reflected part of the light. This part is the most important when rendering smoke.
Source (MXS: darg) - The source channel passed to the shader.
Texture (MXS: dtxt) - If the source channel is set to "Texture", this slot specifies the texture
Reset - resets the settings to their default values
Modulate (MXS: mod_d) - when the Source is not Texture, this check box allows the Source to be multiplied by the texture in the Texture slot.
Simple color (MXS: simple_color) - If the source is Simple Color this value is used.
Particle mode secondary bounces (MSX: pmbounces) - when checked this option optimizes the calculation of GI for the smoke. In this mode the opacity is interpreted as a probability for absorption of the ray - like photons in real light.
Light cache (MXS: lightcache) - Enables cashing of the lighting for each point of the grid.
Scattering correction (MXS:difmul, noscatter) - Alows the user to disable the scattering of the rays in the volume when GI is used and to select how to the light will be calculated. When the scattering is disabled the additional multiplier can be used to adjust the the brightness of the diffuse color.
Enabled - the scattering is enabled
Disabled - the scattering is disabled and the multiplier is used to correct the brightness
Analytic - an analytic foruma is used to calculate the contribution of the scattering to the illumination
Analytic+shadows - same as Analytic but geometry is also affected via the shadows
Color gradient (MXS: dcolorx_s,dcolorx_t, dcolorx_v, dcolory_s, dcolory_t, dcolory_v) - The color of the smoke as a function of the selected channel's value.