In each group, name any U.S. President which matches the first category to reveal the second category, then name any U.S. President which applies to both categories to reveal a third, and so on.
Got stuck on the yellow category...guessed Adams the whole way then somehow read last name as 'first name' in the last category, kept typing Jefferson and wondering why it wasn't accepted.
I'm thinking it's unnecessary to instruct not to include living people in a question about those who died before age 75!
I missed Coolidge, darn it.