Keep in mind that wire colors are basically used so the next electrician will know what was done in the past. I've run into many things that were not code, probably done to save on copper/cost. Always read with a meter to be sure what you are up against. For example, if the house is wired with romex. This is a brand name/slang but one used widely in my area & industry to describe the normal house wiring with a rubber insulation, it will have 2 or 3 insulated wires (red-black-white) and a bare ground inside one covered/insulated cable. In many cases we electricians will use what ever color wires are in the cable and not run an extra to save time effort & money. It would not be uncommon to find a hot white wire, say going to a switch. If the electrician is awake/thinking that day he/she might or might not wrap a piece of red or black tape at the end to give you a clue but some people do not. The jest is never assume the colors to be the end all. Little alamo electro doesn't really care what color that covering is over the copper. He will run like he** on any color available
PS. I've had to straighten problems out for relatives, neighbors and friends many times, where they tried to change out a switch, fixture or ceiling fan, get all confused over wire colors and give up. Had they understood the things I posted here they would have made it without my help. I don't remember charging anyone over a simple problem like that. Of course those were on a more personal level, usually. Sometimes I could get them straight over the phone but that can be a tough call.