Hello,
Please, take into account that we are theme developers, not CSS teachers. Our support helps with questions related to theme options/bugs.
Read docs to get detailed information about your question
The SVG specification decides strictly between attributes that are properties and other attributes. The former can be modified with CSS, the latter not.
https://developer.mozilla.org/en-US/docs/Web/SVG/Tutorial/Fills_and_Strokes#Using_CSS
Regards