Do you like these, TillY. There seem to be several possible answers for some. I think your Pink answer is right but I'm sure my pool ball answer is valid too. I think this H, I, J, .....N can't be a simple as I being a vowel. Wondered about chemical symbols but that didn't work
Another possibility for odd one out of H, I, J, K, L, M, N is K as it's the only one in the list that doesn't appear in the names of the months of the year
The question does appear in a children's Intelligence Tests book when you google it but I can't access the relevant page