hi, this is a bug,it will be fixed in 3.3.0.
If needed, you can temporarily modify the file color.ts,
file:color.zip (6.0 KB)
file path: \3.1.0\resources\resources\3d\engine\cocos\core\math\color.ts
Remember to compile the engine after modifying it, for reference: https://docs.cocos.com/creator/3.1/manual/en/advanced-topics/engine-customization.html?h=engine
Then modify the transparency by modifying the color tag, for example.
Normal: <color=#ff0000>Red Text
Modified: <color=#ff000003>Red Text
The last two digits of color represent the transparency value, and the color transparency hexadecimal table is as follows:
Sorry for the late reply.
we have fixed it in 3.3.0 version, currently 3.3.0 version is not yet released, you can fix it by referring to this pr and making changes: