[HDRP] Remove alpha from local volumetric fog color field

com.unity.render-pipelines.high-definition/CHANGELOG.md

@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Fixed range fields for depth of field (case 1376609).
 - Fixed exception on DLSS when motion vectors are disabled (case # 1377986).
 - Fixed decal performances when they use different material and the same draw order.
+- Fixed alpha channel display in color picker in Local Volumetric Fog component (the alpha is not used for the fog) (case 1381267).
 
 ### Changed
 - Optimizations for the physically based depth of field.

com.unity.render-pipelines.high-definition/Runtime/Lighting/VolumetricLighting/LocalVolumetricFog.cs

@@ -8,6 +8,7 @@ namespace UnityEngine.Rendering.HighDefinition
     public partial struct LocalVolumetricFogArtistParameters
     {
         /// <summary>Single scattering albedo: [0, 1]. Alpha is ignored.</summary>
+        [ColorUsage(false)]
         public Color albedo;
         /// <summary>Mean free path, in meters: [1, inf].</summary>
         public float meanFreePath; // Should be chromatic - this is an optimization!