A "principle" is a truth that is the foundation of a belief system. It is considered objective and unchangeable. A "value" is a person's personal belief for or against something, able to change and subjective. Author Stephen Covey indicated that all people have values, even criminals. He also noted that principled-driven people typically develop their values to align with principles.
A person can have individual principles, but principles are also collectively agreed upon by society. Laws that make murder and robbery illegal are based on the collective view of society that it is principally wrong to kill or steal. A person may tell the truth out of principle, even in a situation where it brings personal harm or adversely affects a friend. Rules and standards are often used as synonyms for principles.
A value is neither inherently right nor inherently wrong. It is an individual or group's perspective on a topic or issue. American values are largely divided along political lines. Conventional Republicans have more conservative societal values and favor pro-business policies. Conventional Democrats often have more liberal social values and favor policies that support social assistance programs. One person might value wealth and power, while another values independence and adventure. These aren't principles because they aren't absolute standards or right ways of doing things.