Is cold chicken breast done?
There is no way of knowing. The importance of cooking for food safety comes down to log reduction of pathogens.* Without accurately knowing the exact temperature that the meat reached and for how long it was held there, you can't known if it cooked long enough to be safe. 

Additionally, you can't count on color, texture, or juices to indicate how cooked a piece of meat is - acidity, age of the meat, etc can play a large role in the appearance of meat. Typically, yes, white meat with clear juices is cooked... but not always.

*: In case the source goes down some day - table of 6.5 and 7 log reduction times for salmonella, at given temperatures. Low end is 130F/54.4C 121 minute for 7 log reduction. High end is 158F/71.1C 0 seconds for 7 log reduction. That is, you will reduce the count of salmonella to 1/10 millionth at the given cook time and temperature. This is why we tell people to cook pork and chicken to 165F - it instantly kills any salmonella in the meat. Salmonella is a very heat tolerant microbe, so if we've performed a 7 log reduction on it, we've done an even larger reduction on other harmful microbes. All of this information is super useful if you ever decide to sous vide meat.