Dark mode is a good shibboleth for who’s old. I’ve seen it working with people under 30. All the young folk have dark mode. The old folk mostly use light, with

Dark mode is a good shibboleth for who’s old. I’ve seen it working with people under 30. All the young folk have dark mode. The old folk mostly use light, with some using dark high contrast. If you have an interview with a person and they use light, it can be a proxy for age to help weed out the gray beards.