Sometimes tags are added incorrectly

Hi,
English is not my primary language, so please excuse me if I am not very clear on my first attempt to explain what I experience.
I have rules, which Add tags to files. For instance, one tag might be a purple tag named MyTag.
Sometimes, it seems that a tag is indeed added to the file, but it is only a Purple tag (named Purple), instead of MyTag: the tag's colour is correct but not the tag's label.
The Purple tag does not exist before added to the file (I have deleted all colour named tags).
Has anyone already encountered this behaviour?
Thanks
English is not my primary language, so please excuse me if I am not very clear on my first attempt to explain what I experience.
I have rules, which Add tags to files. For instance, one tag might be a purple tag named MyTag.
Sometimes, it seems that a tag is indeed added to the file, but it is only a Purple tag (named Purple), instead of MyTag: the tag's colour is correct but not the tag's label.
The Purple tag does not exist before added to the file (I have deleted all colour named tags).
Has anyone already encountered this behaviour?
Thanks