In Settings choose Accessibility
Scroll to bottom to Accessibility Shortcut
Note at the top it gives specific phone-dependent instructions for engaging the shortcuts.
Put a check on Color Filters
Go back to Accessibility and go to Display & Text Size (near the top)
From Display and text size, click Color Filters, and turn it on at the top, Check mark Color Tint.
Slide HUE all the way right to get Red, then choose INTENSITY level with slider above that you want—it will have to be pretty far right to be effective.
Done. Can close Settings.
Then you can turn this on and off with a triple click of the side button or home button on your phone, depending on model.
Note if you have other Accessibility shortcuts checked, you choose between them with the triple click.