What things should you never say to/ask a person of colour, and why?

This in my opinion is how a White thinks sees another civilised being whom he apparently calls a Black:

1. Watcha doing in my country Nigga ( slang ) . 

2. You can buy your food with me but not eat with me.

3. You get what I chose to not take.

4. You are an equal for me but I don't want my child to talk to yours.

These are forms of prejudice that exist in society today.  Majority accept their prejudice and openly declare themselves as rightful to derogate the Black and condemn his birth. On the other hand a section claims to see everyone as their equal but either see this as a gesture that needs to be acknowledged or have subconscious perceptions in them that only ignores racism at the superficial level and not from their true cognitive processes.