You know to what I am referring. It's the blue background with yellow text that inexplicably became popular at some point early in PPT history. It's not even a good color scheme so I have no idea why it became so popular, but if you see 10-15 year old slides, they are often in this style. That means you can tell when people steal old slides from Google Images or else haven't updated their slides for a decade. I went to a seminar today that used this color scheme for the whole presentation. She was a young presenter so I don't think it's a case of not updating slides, and the whole lecture was that way, and I don't think she borrowed them all, so why in the heck would she pick that color scheme? Did she want to look like she hasn't made new slides for years?
This cartoon might explain it: