If you're copy and pasting from outside sources, make sure you're clearing the format after you copy and paste.
First highlight the text you just pasted > The 'Double A' icon is the text formatting icon
From left to right, the icons are 'Text Size' > 'Text Color' > 'Text Highlight Color' > 'Text Font'
'Text Color' is more than likely what needs to be cleared.
Caution: If you set the color to White but someone chooses a White theme for their app, they won't be able to see the text. Just simply 'Remove color' so that all themes can see the text.