Created attachment 193267 [details] Example document for custom shape with line geometry Open attached pptx-document. It contains an extruded free form line. I have added a screenshot which shows the line in point edit mode, so that you can see, that it is indeed a Bezier curve. And the screenshot shows, how the extrusion is rendered in PowerPoint. Such free from line is imported as custom shape. Depending on your LO version, the shape is extruded or not. Toggle extrusion if necessary, so that it is in 3D. Try to set the extrusion color. That is "3D Color" in the "3D-Settings" dialog. Erro: Setting an extrusion color has no effect. I have taken the way via pptx-file because that is an easy way to generate such custom shapes. Otherwise you need to edit the file text of an odp document, because LibreOffice has no UI to generate such documents. But the error is not in PPTX import.
I reproduce To reproduce, select the object and in the 3D effects toolbar that appears, click the dropdown of the last button, 3D Color, to select a color. Version: 25.2.0.0.alpha0+ (X86_64) / LibreOffice Community Build ID: 6adfa5811d4dc65b28544169825b88846bc55596 CPU threads: 8; OS: Windows 10 X86_64 (10.0 build 19045); UI render: Skia/Raster; VCL: win Locale: fi-FI (fi_FI); UI: en-GB Calc: CL threaded