In the styles.xml of the ODF XML the background color attribute @draw:fill-color is being used as default style for the graphics family - for instance the default fill for all frames, see https://bugs.documentfoundation.org/attachment.cgi?id=120367 (bug 95660). Its usage can visiualy confirmed by testing the ODT in LO Writer. Unfortunately, the ODF spec states: "It is used only if the draw:fill 20.118 attribute has one of the values solid or hatch.", see https://docs.oasis-open.org/office/OpenDocument/v1.3/os/part3-schema/OpenDocument-v1.3-os-part3-schema.html#property-draw_fill-color But @draw:fill color is misssing, while the color is shown. Please add the attribute @draw:fill!
Created attachment 188181 [details] Red Square Added a rectangle and changed background color to red. The draw:fill attribute is missing while color is shown.