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

polygon - Changing categorized style color simultaneously in QGIS

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

Change the colour of a polygon in QGIS

Filling polygon with 2 different colours representing 2 different

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Change both border and fill colors in one place in QGIS 3.0

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