But all in all it is a good page for people with poor vision.
No low-contrast and no white background, which are both considered bad on screens.
Yes, the white on black is fine. I checked the #8a7ae2 purple (http://webaim.org/resources/contrastchecker/) and, surprisingly, it passes WCAG AAA guidelines. I say "surprisingly" because it hurts my eyes. I think jumping between the alternating white and purple is what does it.