This is the only question I've found similar to mine even so it is not 100% clear as the solution seems to be static for that key and it's not explained very well: How to extend the tinymce validation rules for the style tag?

Right now I'm using TinyMCE in my project and the problem is when I have for example an inline style like:

style="height: 12mm; border: solid white 3px; background-color: [Category.FieldNumber01]"

The background changes all to lowercase, this happens with any custom style I want to use that has uppercase:

background-color: [category.fieldnumber01]

Is there a way that might be on the configuration or a function to make TinyMCE ignore style uppercases?