I don't see well so the white font with a light blue background is invisible to me. I don't really do the dark option well either. I am old (a great-grandmother actually) and usually I can figure stuff out on my own so this is frustrating. Making the font bold helps a bit but I would prefer to either make the highlight color darker or make the font black if possible.
EDIT:
Cirtel's answer helped to narrow this down the most. It's not the highlighter color it's the white font. I changed the highlight color to a dark grey and was able to see the text clearly.