Libya's, Angola's and PNG's flags are all on a 50% background of black, all of them less a small amount for PNG's stars, Angola's half a hammer-and-sickle and Libya's crescent-and-star. Are you sure it's PNG?
Federated States of Micronesia probably has more blue. The area covered by their 4 white stars will be the same as a single star twice the height and width of one of their small stars; that larger white star looks to me like it would be smaller than Somalia's.
You are right. Good spot. I have updated the quiz ,thanks. I used a pixel counting tool and got to 98% for Micronesia and 97% for Somalia. I used the flags from Wikipedia.