cant we use inline css to skuid xml page?

Can you elaborate what you’re wanting to do? You can add CSS to a page and what you add will show up in the XML.

one field editor has 4 section i like to color all 4 section with different.
And Every field has unique id i like use css on every unique id

You can certainly do that.
https://docs.skuid.com/v10.0.4/en/skuid/css/