Let's say there was a bunch of kids cutting out hearts for Valentine's Day and some of them were different colors you might say "Julia's heart is red", "Carly's heart is purple" :). Out of context, many things sound weird.

Welcome to Duolingo

I mean you could during an autopsy.

true

dangerous heart

In my mind a living heart is red

I guess it is because of possessive case in both the languages (english and hindi)