They are, because people having varying numbers of Rods and cones in their eyes, it causes people to see colours differently.
Also there is a theory that everyone sees, for example, the colour red differently eg Red=yellow, but because we’ve been taught that, that specific colour is red, no one knows if everyone is seeing the same colour as another person.
Did you know on average the human body needs 8 positive touches a day to survive? This includes: hand shakes, a hand on the shoulder, a hug, a kiss. etc. So you people saying, people that are depressed are just upset because they don’t get attention, in a way, you’re right, when your body lacks positive touches it can stunt your growth and effect your mental and emotional development. Give a hug.