Changing text color for posts using Gamepress theme

It appears that the color is set directly in the editor, overriding any CSS. You may have to re-edit your posts to remove the manually set colors.

see https://pix.toile-libre.org/upload/original/1469391659.png

you could try forcing the white text coor by adding a CSS like this via a ‘custon CSS’ plugin:

.hentry p span { color: white!important; }