I’m not sure why but interfaces that consist only of red and black text look very unpleasant to me. I felt the same way when Apple started using red and black

I’m not sure why but interfaces that consist only of red and black text look very unpleasant to me. I felt the same way when Apple started using red and black for things like iOS calendar highlights. I suspect the reason is that they are both strong colors that compete for attention: black-on-white is high contrast and red is a color that generally “jumps out” from the page due to the eye’s perception of red. To keep the colors from competing, one of the text colors should be softer (and if they must have “red”, they should soften it to something that is closer to pastel or pink).