You can read in the Qt documentation "If you create a new widget we strongly recommend that you use the colors in the palette rather than hard-coding specific colors".

Unfortunately, QHexEdit does not yet adhere to this specification. As a result, when the parent theme changes, the QHexEdit widget only partially adapts. In reality, there is a terrible mess that you don't want to look at. However, using the palette as a design element means that some properties should be omitted. This affects the properties:

• addressAreaColor
• addressFontColor
• asciiAreaColor
• asciiFontColor
• hexFontColor
• highlightingColor

So the interface is getting simpler, which is a good thing. However, it is unfortunate that these changes are not backwards-compatible and may require changes to the surrounding program.