polygon - Changing categorized style color simultaneously in QGIS

I work with this polygon: and i need that all features will be with border line only without fil colors. I seek for a way to do it simultaneously to all the categorized features, and not treat every

Symbolising data - QGIS Tutorial

polygon - Multiple styles in one layer in QGIS - Geographic

layouts - Selecting different colors for touching polygons in

1.8. QGIS visualization for vectors — GIS4Schools documentation

QGIS no longer loads styles from PostGIS · Issue #39850 · qgis

How to draw,add split merge and change style color transparency of

Modern Art is nothing compared to the random colours that QGIS

style - QGIS ordering categorized styling doesn't work

3.3. Lesson: Classification — QGIS Documentation documentation