Adjectives normally follow the noun in Irish. Cat bán - "a white cat", bosca mór - a big box", bainne géar - "sour milk".
To use a noun like cat as an adjective, you use the genitive, so "cat milk" (or "cat's milk") is bainne cait (or bainne an chait for "the cat's milk").
Since this is the first time we have seen "sé" meaning "six", I feel it should be in orange as a "new word". I understand that we have seen it in the past meaning "he", and the alternate translation of "six" is probably listed in those lessons when hovering over the word. However, "sé" was introduced so long ago, and used so many times since in the context of meaning "he", that this is effectively a new term for us at this point. One important point is that in the mobile app only new words in orange show their definition when tapped on (unlike in the desktop version where I can see the definition of non-new words by hovering over them).
Hey, Blackhawks! Chicago! (Sorry. Got carried away.)
Yup, I got confused by that too, and I thought counting was one thing I had down pat. I think its because we have been focussing so heavily on the pronoun that shifting at first comes as a shock. Next time it is more natural. (And hey! Chicago! Got to go back some day.)
In most cases, you don't pluralize a noun after a number in Irish.
Ceannaím trí phláta nua
"three plates", but plataí is the plural "plates".
Tá ceithre lítear ann.
"four litres", but lítir (with a fada on the first í) is the plural "litres".
Tá cúig leabhar agam anois
cúig leabhar, but leabhair is the plural "books".