Use Source Colors9 under Hull Parameters affects only those viewer functions that support user-defined point colors. This option causes the user-defined point colors in the Excel file to override the solid color settings for Show Points1 and Fill Volume3 (Viewer Parameters) and Show Hull Fill8.
In the case of Fill and Hull Fill, the point colors are used for blending the fill area between points (between vertices), giving convex hulls and mesh surfaces smooth color gradients. When Use Source Colors9 is unchecked, user-defined colors are ignored.
Source colors disabled (left) vs. source colors enabled (right); left hull is a uniform fill, the point colors are ignored.