Where you can do so, use your browser's Reader Mode.
It's possible to further tune Reader Mode (using userContent.css) to your personal preferences, though I believe you can also directly set colours, typically to Black-on-White, White-on-Black, or a Sepia (usually dark brown on smokey white) theme.
When using a full-powered desktop, I'll use Stylish to adjust site CSS to my preferences, usually nuking distractions, though also occasionally modifying colour schemes. That's problematic as there are often many elements to change (nuking all but the principle payload has the side benefit of simplifying this problem).
It's possible to further tune Reader Mode (using userContent.css) to your personal preferences, though I believe you can also directly set colours, typically to Black-on-White, White-on-Black, or a Sepia (usually dark brown on smokey white) theme.
When using a full-powered desktop, I'll use Stylish to adjust site CSS to my preferences, usually nuking distractions, though also occasionally modifying colour schemes. That's problematic as there are often many elements to change (nuking all but the principle payload has the side benefit of simplifying this problem).