In Colombian culture it's generally best to avoid discussing politics or the present armed conflict in public, except with well-known acquaintances or relatives that have your trust and confidence. In general, nobody will react with violence to different opinions, but the hearts of Colombians suffer deeply remembering all the victims of the political and narcotics wars of past and current conflicts.
Accordingly, do not approach the subjects of drug wars or political turmoil in your first conversation with a Colombian; this can really grate on their nerves, since Colombians are acutely aware of their country's bad reputation, and tactless remarks about the history of violence might earn you a snide remark (likely regarding your country of origin) and an abrupt end to the conversation.
However, Colombians will eventually become willing to discuss these topics once they feel comfortable enough with someone.
Colombians are more formal than much of Latin America. Make a point to say "please" ("Por favor" or "Hágame el favor") and "thank you" ("muchas gracias") for anything, to anyone. When addressed, the proper response is "¿Señora?" or "¿Señor?".
In parts of the country (especially Boyacá) Colombians can be formal to the point of anachronism, calling strangers "Su merced" (your Mercy!) in place of usted.
The one (much) more informal part of the country is along the Caribbean coast, where referring to people just as "chico" can be more the norm—but take your cues from those around you.
Race is not a hot issue in Colombia since whites, criollos, and mestizos (mixed race) blend naturally with natives and Afro-Colombians in everyday life (education, living, politics, marriage).
Differences between white foreigners are not dwelled upon: expect to be called "gringo" even if you are, say, Russian.
Unless context includes anger, it's not meant to be offensive. If you are black, you will probably be referred to as "negro" or "moreno," which also are not considered at all offensive.
Asians are usually called "chino" (Chinese), regardless of actual background. Confusingly, Colombians also occasionally refer to children as chinos ("kids"); this use comes from Chibcha, an indigenous language.
Even more confusingly, Colombians refer to blondes and redheads as "monos" (monkeys). It sounds offensive but actually ranges from neutral to affectionate.
Colombians have the mannerism of pointing to objects with their chins; pointing to a person or even an object with your finger can be considered rude.
Avoid indicating a person's height using your hand palm down, as this is considered reserved for animals or inanimate objects. If you must, use your palm facing sidewards with the bottom of the hand expressing the height.
Colombians dance a lot. Anyone will be glad to teach you how to dance, and they will not expect you to do it correctly since they have been practising every weekend for most of their lives. Colombian night life centres mostly on dancing and bars where people sit or stand are less common outside major cities.
When dancing, despite what you might think of all the sensual movements of men and women, people just enjoy music and dancing and are normally not intended as sexual encounters or as sexual signs.
Here you could find salsa being danced at a children's "piñata" party, or even at parties for older people. North Americans and Europeans could find this odd or confusing because of the use of salsa and Latin rhythms in their countries.
A Colombian dancing innocently could be misinterpreted, and in general, Colombian women or men are not "easy" just because of the way they dance. It is applied in the same way as in Brazil an almost-naked "garota" dancing samba in the carnival is not inviting you to have sex with her but inviting you to enjoy, to be happy, to join in the celebration, to join the exuberant shedding of inhibitions.
Regarding religion, most Colombians are Catholic, and it´s important to them to keep certain ceremonies and respect for all things related to religion.
You could visit great architectural churches, even going inside, but taking pictures may be considered disrespectful during a mass celebration. Young people are more open to learning about other religions and debate on this subject, and you may even find a lot of them who may consider themselves as lapsed, non-practising Catholics or even non-religious.