The Modern UI has poor contrast in many elements, in particular the issue lists. There are tons of light-blue links on light-grey background. You can take the colors (link foreground color: #337ab7, table background color: ranges from #dddddd to #ffffff), put them into e.g. http://webaim.org/resources/contrastchecker/ and you will see that this color combination fails at normal text sizes. For #ffffff it barely passes, but for any darker background (like in the issue lists) it fails.

I know these low-contrast color schemes are modern and slick and everything, but in the long run they ruin people's eyes and people who already have impaired eyesight will have a very hard time reading the texts in MantisBT. I am not visually impaired but even I have the feeling that reading the issue lists on my_view_page.php strains my eyes more than it should.
Pre-2.0 Mantis versions were much more accessible in this regard. Please consider improving color contrast in the Modern UI scheme.