Browser dark mode changes black text to white

I realize I'm replying to this several years later, but I was having a similar issue and found a solution--or at least, I was able to make it show the text. It turns out that the issue was not Dark Mode, but a setting in Chrome called "Auto Dark Mode for Web Contents." This is a "Experiment" feature in Chrome, which appears to be where users submit and share projects/ideas/tweaks.

Anyway, if you type "chrome://flags" into the Chrome address bar, you can search for "dark." There, you can make sure the "Auto Dark Mode for Web Contents" is set to "Default." I've toggled this on and off between "Default" and "Enabled," and the white text issue comes up when the setting is "Enabled." 

You have to relaunch Chrome and maybe close/reopen the course, but it should go back to normal font colors.