The expression "nail colors to mast" traditionally refers to the act of tying a flag to the top of a ship's mast to signify its identity. However, the phrase has evolved to include a broader meaning of standing up for one's beliefs or committing to a particular course of action. There are several synonyms for "nail colors to mast" including "planting a flag," "declaring one's allegiance," "taking a stand," "showing one's colors," and "standing firm." All of these expressions convey a sense of resolve and determination to stay true to a cause or belief, even in the face of opposition.