Maybe the way they look.

Nicola, all countries are dangerous depends of the site where you go, if you ask me I say: Colombia is dangerous but also is safe because the people is very friendly and we love the turists, We are very hospitable. Is true, in many places if the "bad boys" see turists, they will want take advantage however not all places on Colombia. I therefore recommend if you will travel to Colombia you will enjoy your life but also you need to be cautious.
You need meeting good people and leave that they give some good advices for you.

(sorry for my bad english skills, I need to practice :P)

Everyone will say "the happiness is most important thing" and in many case is obvious, but not all feel these words.
In my opinion depend of the situation in which you are, this answer is very difficult of find because is easy to say "the happiness is very important" but in my opinion who can living with a bit of money and say "I´m soo happy" this person feel the answer.

Con mucho gusto Ungu :D

Ungu, You know many things about Colombia :D that is cool

The case of pronoun YOU (singular) is more common say USTED (formal) when you don´t meet the people, but in many case and in many parts of Colombia when you want be friendly and you meet the people you can use the pronoun TU (informal) depends of the conjugation. For example

Usted: ¿Usted tiene un lapiz que me preste?

Tu:  ¿Tu tienes un lapiz que me prestes?