In your article details I can see you have probably copy/pasted the content from somewhere else (another page, or word ...)
This have included forced inline styles for the text ...

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This inline style is overwriting the global settings of your article details page ...

Solution: Clear the styles after copy/pasting from word or web pages
To clear all the inline styles select all the text in the blod editor and click on Tx icon to clear all styles
Then you can add formatting (bold, size, ...) but don't set a text color if you want to have your global style applied ...